diff --git a/CHANGELOG.md b/CHANGELOG.md
index 058deb3fa79..1e2ea008c1f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,9 +8,14 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased]
 
+### Added
+
+- `trace.WithIDGenerator()` `TracerProviderOption`. (#1363)
+
 ### Changed
 
 - Move the OpenCensus example into `example` directory. (#1359)
+- Moved the SDK's `internal.IDGenerator` interface in to the `sdk/trace` package to enable support for externally-defined ID generators. (#1363)
 - `NewExporter` and `Start` functions in `go.opentelemetry.io/otel/exporters/otlp` now receive `context.Context` as a first parameter. (#1357)
 - Zipkin exporter relies on the status code for success rather than body read but still read the response body. (#1328)
 
diff --git a/sdk/trace/config.go b/sdk/trace/config.go
index 3fd37de24c9..42b1851f833 100644
--- a/sdk/trace/config.go
+++ b/sdk/trace/config.go
@@ -16,7 +16,6 @@ package trace // import "go.opentelemetry.io/otel/sdk/trace"
 
 import (
 	"go.opentelemetry.io/otel/sdk/resource"
-	"go.opentelemetry.io/otel/sdk/trace/internal"
 )
 
 // Config represents the global tracing configuration.
@@ -25,7 +24,7 @@ type Config struct {
 	DefaultSampler Sampler
 
 	// IDGenerator is for internal use only.
-	IDGenerator internal.IDGenerator
+	IDGenerator IDGenerator
 
 	// MaxEventsPerSpan is max number of message events per span
 	MaxEventsPerSpan int
diff --git a/sdk/trace/id_generator.go b/sdk/trace/id_generator.go
index 3a4abe62833..e60a421cde9 100644
--- a/sdk/trace/id_generator.go
+++ b/sdk/trace/id_generator.go
@@ -15,23 +15,30 @@
 package trace // import "go.opentelemetry.io/otel/sdk/trace"
 
 import (
+	"context"
+	crand "crypto/rand"
+	"encoding/binary"
 	"math/rand"
 	"sync"
 
 	"go.opentelemetry.io/otel/trace"
-
-	"go.opentelemetry.io/otel/sdk/trace/internal"
 )
 
-type defaultIDGenerator struct {
+// IDGenerator allows custom generators for TraceID and SpanID.
+type IDGenerator interface {
+	NewIDs(ctx context.Context) (trace.TraceID, trace.SpanID)
+	NewSpanID(ctx context.Context, traceID trace.TraceID) trace.SpanID
+}
+
+type randomIDGenerator struct {
 	sync.Mutex
 	randSource *rand.Rand
 }
 
-var _ internal.IDGenerator = &defaultIDGenerator{}
+var _ IDGenerator = &randomIDGenerator{}
 
 // NewSpanID returns a non-zero span ID from a randomly-chosen sequence.
-func (gen *defaultIDGenerator) NewSpanID() trace.SpanID {
+func (gen *randomIDGenerator) NewSpanID(ctx context.Context, traceID trace.TraceID) trace.SpanID {
 	gen.Lock()
 	defer gen.Unlock()
 	sid := trace.SpanID{}
@@ -39,12 +46,22 @@ func (gen *defaultIDGenerator) NewSpanID() trace.SpanID {
 	return sid
 }
 
-// NewTraceID returns a non-zero trace ID from a randomly-chosen sequence.
-// mu should be held while this function is called.
-func (gen *defaultIDGenerator) NewTraceID() trace.TraceID {
+// NewIDs returns a non-zero trace ID and a non-zero span ID from a
+// randomly-chosen sequence.
+func (gen *randomIDGenerator) NewIDs(ctx context.Context) (trace.TraceID, trace.SpanID) {
 	gen.Lock()
 	defer gen.Unlock()
 	tid := trace.TraceID{}
 	gen.randSource.Read(tid[:])
-	return tid
+	sid := trace.SpanID{}
+	gen.randSource.Read(sid[:])
+	return tid, sid
+}
+
+func defaultIDGenerator() IDGenerator {
+	gen := &randomIDGenerator{}
+	var rngSeed int64
+	_ = binary.Read(crand.Reader, binary.LittleEndian, &rngSeed)
+	gen.randSource = rand.New(rand.NewSource(rngSeed))
+	return gen
 }
diff --git a/sdk/trace/internal/internal.go b/sdk/trace/internal/internal.go
deleted file mode 100644
index 08898efae35..00000000000
--- a/sdk/trace/internal/internal.go
+++ /dev/null
@@ -1,24 +0,0 @@
-// Copyright The OpenTelemetry Authors
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-// Package internal provides trace internals.
-package internal
-
-import "go.opentelemetry.io/otel/trace"
-
-// IDGenerator allows custom generators for TraceId and SpanId.
-type IDGenerator interface {
-	NewTraceID() trace.TraceID
-	NewSpanID() trace.SpanID
-}
diff --git a/sdk/trace/provider.go b/sdk/trace/provider.go
index 2ed731ac928..4c6e6e2ecf0 100644
--- a/sdk/trace/provider.go
+++ b/sdk/trace/provider.go
@@ -66,7 +66,7 @@ func NewTracerProvider(opts ...TracerProviderOption) *TracerProvider {
 	}
 	tp.config.Store(&Config{
 		DefaultSampler:       ParentBased(AlwaysSample()),
-		IDGenerator:          defIDGenerator(),
+		IDGenerator:          defaultIDGenerator(),
 		MaxAttributesPerSpan: DefaultMaxAttributesPerSpan,
 		MaxEventsPerSpan:     DefaultMaxEventsPerSpan,
 		MaxLinksPerSpan:      DefaultMaxLinksPerSpan,
@@ -231,3 +231,10 @@ func WithResource(r *resource.Resource) TracerProviderOption {
 		opts.config.Resource = r
 	}
 }
+
+// WithIDGenerator option registers an IDGenerator with the TracerProvider.
+func WithIDGenerator(g IDGenerator) TracerProviderOption {
+	return func(opts *TracerProviderConfig) {
+		opts.config.IDGenerator = g
+	}
+}
diff --git a/sdk/trace/sampling_test.go b/sdk/trace/sampling_test.go
index 3c998773327..6ae4afff390 100644
--- a/sdk/trace/sampling_test.go
+++ b/sdk/trace/sampling_test.go
@@ -15,6 +15,7 @@
 package trace
 
 import (
+	"context"
 	"fmt"
 	"math/rand"
 	"testing"
@@ -168,7 +169,7 @@ func TestTraceIdRatioSamplesInclusively(t *testing.T) {
 		numSamplers = 1000
 		numTraces   = 100
 	)
-	idg := defIDGenerator()
+	idg := defaultIDGenerator()
 
 	for i := 0; i < numSamplers; i++ {
 		ratioLo, ratioHi := rand.Float64(), rand.Float64()
@@ -178,7 +179,7 @@ func TestTraceIdRatioSamplesInclusively(t *testing.T) {
 		samplerHi := TraceIDRatioBased(ratioHi)
 		samplerLo := TraceIDRatioBased(ratioLo)
 		for j := 0; j < numTraces; j++ {
-			traceID := idg.NewTraceID()
+			traceID, _ := idg.NewIDs(context.Background())
 
 			params := SamplingParameters{TraceID: traceID}
 			if samplerLo.ShouldSample(params).Decision == RecordAndSample {
diff --git a/sdk/trace/span.go b/sdk/trace/span.go
index 5ee2a8bb8c9..fb3c6382c94 100644
--- a/sdk/trace/span.go
+++ b/sdk/trace/span.go
@@ -15,6 +15,7 @@
 package trace // import "go.opentelemetry.io/otel/sdk/trace"
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"reflect"
@@ -306,7 +307,7 @@ func (s *span) addChild() {
 	s.mu.Unlock()
 }
 
-func startSpanInternal(tr *tracer, name string, parent trace.SpanContext, remoteParent bool, o *trace.SpanConfig) *span {
+func startSpanInternal(ctx context.Context, tr *tracer, name string, parent trace.SpanContext, remoteParent bool, o *trace.SpanConfig) *span {
 	var noParent bool
 	span := &span{}
 	span.spanContext = parent
@@ -314,10 +315,13 @@ func startSpanInternal(tr *tracer, name string, parent trace.SpanContext, remote
 	cfg := tr.provider.config.Load().(*Config)
 
 	if parent == emptySpanContext {
-		span.spanContext.TraceID = cfg.IDGenerator.NewTraceID()
+		// Generate both TraceID and SpanID
+		span.spanContext.TraceID, span.spanContext.SpanID = cfg.IDGenerator.NewIDs(ctx)
 		noParent = true
+	} else {
+		// TraceID already exists, just generate a SpanID
+		span.spanContext.SpanID = cfg.IDGenerator.NewSpanID(ctx, parent.TraceID)
 	}
-	span.spanContext.SpanID = cfg.IDGenerator.NewSpanID()
 	data := samplingData{
 		noParent:     noParent,
 		remoteParent: remoteParent,
diff --git a/sdk/trace/trace.go b/sdk/trace/trace.go
deleted file mode 100644
index 302ca13cf72..00000000000
--- a/sdk/trace/trace.go
+++ /dev/null
@@ -1,31 +0,0 @@
-// Copyright The OpenTelemetry Authors
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package trace // import "go.opentelemetry.io/otel/sdk/trace"
-
-import (
-	crand "crypto/rand"
-	"encoding/binary"
-	"math/rand"
-
-	"go.opentelemetry.io/otel/sdk/trace/internal"
-)
-
-func defIDGenerator() internal.IDGenerator {
-	gen := &defaultIDGenerator{}
-	var rngSeed int64
-	_ = binary.Read(crand.Reader, binary.LittleEndian, &rngSeed)
-	gen.randSource = rand.New(rand.NewSource(rngSeed))
-	return gen
-}
diff --git a/sdk/trace/trace_test.go b/sdk/trace/trace_test.go
index da9e46ae323..8ccd44046f8 100644
--- a/sdk/trace/trace_test.go
+++ b/sdk/trace/trace_test.go
@@ -213,7 +213,7 @@ func TestRecordingIsOn(t *testing.T) {
 }
 
 func TestSampling(t *testing.T) {
-	idg := defIDGenerator()
+	idg := defaultIDGenerator()
 	const total = 10000
 	for name, tc := range map[string]struct {
 		sampler       Sampler
@@ -263,9 +263,10 @@ func TestSampling(t *testing.T) {
 			for i := 0; i < total; i++ {
 				ctx := context.Background()
 				if tc.parent {
+					tid, sid := idg.NewIDs(ctx)
 					psc := trace.SpanContext{
-						TraceID: idg.NewTraceID(),
-						SpanID:  idg.NewSpanID(),
+						TraceID: tid,
+						SpanID:  sid,
 					}
 					if tc.sampledParent {
 						psc.TraceFlags = trace.FlagsSampled
diff --git a/sdk/trace/tracer.go b/sdk/trace/tracer.go
index 872c37d84c6..ea90bb65f32 100644
--- a/sdk/trace/tracer.go
+++ b/sdk/trace/tracer.go
@@ -47,7 +47,7 @@ func (tr *tracer) Start(ctx context.Context, name string, options ...trace.SpanO
 		}
 	}
 
-	span := startSpanInternal(tr, name, parentSpanContext, remoteParent, config)
+	span := startSpanInternal(ctx, tr, name, parentSpanContext, remoteParent, config)
 	for _, l := range links {
 		span.addLink(l)
 	}