diff --git a/src/array.jl b/src/array.jl
index 8580ef0..7a98cb5 100644
--- a/src/array.jl
+++ b/src/array.jl
@@ -1,6 +1,6 @@
 ## Common code for CategoricalArray and NullableCategoricalArray
 
-import Base: convert, copy, getindex, setindex!, similar, size, linearindexing
+import Base: convert, copy, getindex, setindex!, similar, size, linearindexing, vcat
 
 # Used for keyword argument default value
 _ordered(x::AbstractCategoricalArray) = ordered(x)
@@ -215,6 +215,14 @@ end
             R = reftype(length(index(A.pool)))
             convert($A{T, N, R}, A)
         end
+
+        function vcat(A::$A...)
+            newlevels, isordered = mergelevels(map(levels, A)...)
+
+            refs = [indexin(index(a.pool), newlevels)[a.refs] for a in A]
+            $A(DefaultRefType[refs...;],
+               CategoricalPool(newlevels, isordered && all(ordered, A)))
+        end
     end
 end
 
@@ -351,3 +359,30 @@ function getindex(A::CategoricalArray, i::Int)
 end
 
 levels!(A::CategoricalArray, newlevels::Vector) = _levels!(A, newlevels)
+
+function mergelevels(levels...)
+    T = Base.promote_eltype(levels...)
+    res = Array{T}(0)
+    isordered = true
+
+    for l in levels
+        levelsmap = indexin(l, res)
+
+        isordered &= issorted(levelsmap[levelsmap.!=0])
+        if !isordered
+            # Give up attempt to order res
+            append!(res, l[levelsmap.==0])
+        else
+            i = length(res)+1
+            for j = length(l):-1:1
+                if levelsmap[j] == 0
+                    insert!(res, i, l[j])
+                else
+                    i = levelsmap[j]
+                end
+            end
+        end
+    end
+
+    res, isordered
+end
diff --git a/test/11_array.jl b/test/11_array.jl
index 8511181..279167d 100644
--- a/test/11_array.jl
+++ b/test/11_array.jl
@@ -576,6 +576,67 @@ for isordered in (false, true)
             @test x[1] === x.pool.valindex[3]
             @test x[2] === x.pool.valindex[1]
             @test levels(x) == ["c", "a", "b"]
+
+
+            # Tests of vcat of CategoricalArray
+            # Test that vcat of compact arrays use a reftype that doesn't overflow
+            a1 = 3:200
+            a2 = 300:-1:100
+            ca1 = CategoricalArray(a1)
+            ca2 = CategoricalArray(a2)
+            cca1 = compact(ca1)
+            cca2 = compact(ca2)
+            r = vcat(cca1, cca2)
+            @test r == vcat(a1, a2)
+            @test isa(cca1, CategoricalArray{Int,1,UInt8})
+            @test isa(cca2, CategoricalArray{Int,1,UInt8})
+            @test isa(r, CategoricalArray{Int,1,CategoricalArrays.DefaultRefType})
+            @test isa(vcat(cca1, ca2), CategoricalArray{Int,1,CategoricalArrays.DefaultRefType})
+            @test ordered(r) == false
+            @test levels(r) == collect(3:300)
+
+            # Test vcat of multidimensional arrays
+            a1 = Array{Int}(2,3,4,5)
+            a2 = Array{Int}(3,3,4,5)
+            a1[1:end] = (length(a1):-1:1) + 2
+            a2[1:end] = (1:length(a2)) + 10
+            ca1 = CategoricalArray(a1)
+            ca2 = CategoricalArray(a2)
+            cca1 = compact(ca1)
+            cca2 = compact(ca2)
+            r = vcat(cca1, cca2)
+            @test r == vcat(a1, a2)
+            @test isa(r, CategoricalArray{Int,4,CategoricalArrays.DefaultRefType})
+            @test ordered(r) == false
+            @test levels(r) == collect(3:length(a2)+10)
+
+            # Test that sortedmerge handles mutually compatible ordering
+            @test CategoricalArrays.mergelevels([6,3,4,7],[2,3,5,4],[2,4,8]) == ([6,2,3,5,4,7,8],true)
+            @test CategoricalArrays.mergelevels([6,3,4,7],[2,3,6,5,4],[2,4,8]) == ([6,3,4,7,2,5,8],false)
+
+            # Test concatenation of mutually compatible levels
+            a1 = ["Young", "Middle"]
+            a2 = ["Middle", "Old"]
+            ca1 = CategoricalArray(a1, ordered=true)
+            ca2 = CategoricalArray(a2, ordered=true)
+            levels!(ca1, ["Young", "Middle"])
+            levels!(ca2, ["Middle", "Old"])
+            r = vcat(ca1, ca2)
+            @test r == vcat(a1, a2)
+            @test levels(r) == ["Young", "Middle", "Old"]
+            @test ordered(r) == true
+
+            # Test concatenation of conflicting ordering. This drops the ordering
+            a1 = ["Old", "Young", "Young"]
+            a2 = ["Old", "Young", "Middle", "Young"]
+            ca1 = CategoricalArray(a1, ordered=true)
+            ca2 = CategoricalArray(a2, ordered=true)
+            levels!(ca1, ["Young", "Middle", "Old"])
+            # ca2 has another order
+            r = vcat(ca1, ca2)
+            @test r == vcat(a1, a2)
+            @test levels(r) == ["Young", "Middle", "Old"]
+            @test ordered(r) == false
         end
     end
 end