diff --git a/src/array.jl b/src/array.jl
index b3c845ed..9116a0b8 100644
--- a/src/array.jl
+++ b/src/array.jl
@@ -1,7 +1,7 @@
 ## Common code for CategoricalArray and NullableCategoricalArray
 
 import Base: convert, copy, copy!, getindex, setindex!, similar, size,
-             linearindexing, unique, vcat
+             linearindexing, unique, vcat, in
 
 # Used for keyword argument default value
 _isordered(x::AbstractCategoricalArray) = isordered(x)
@@ -711,3 +711,17 @@ levels!(A::CategoricalArray, newlevels::Vector) = _levels!(A, newlevels)
 droplevels!(A::CategoricalArray) = levels!(A, unique(A))
 
 unique(A::CategoricalArray) = _unique(Array, A.refs, A.pool)
+
+function in{T, N, R}(x::Any, y::CategoricalArray{T, N, R})
+    ref = get(y.pool, x, zero(R))
+    ref != 0 ? ref in y.refs : false
+end
+
+function in{T, N, R}(x::CategoricalValue, y::CategoricalArray{T, N, R})
+    if x.pool === y.pool
+        return x.level in y.refs
+    else
+        ref = get(y.pool, index(x.pool)[x.level], zero(R))
+        return ref != 0 ? ref in y.refs : false
+    end
+end
diff --git a/src/nullablearray.jl b/src/nullablearray.jl
index 42f3eda2..4def28a1 100644
--- a/src/nullablearray.jl
+++ b/src/nullablearray.jl
@@ -1,4 +1,4 @@
-import Base: convert, getindex, setindex!, similar
+import Base: convert, getindex, setindex!, similar, in
 using NullableArrays: NullableArray
 
 ## Constructors and converters
@@ -137,3 +137,21 @@ levels!(A::NullableCategoricalArray, newlevels::Vector; nullok=false) = _levels!
 droplevels!(A::NullableCategoricalArray) = levels!(A, _unique(Array, A.refs, A.pool))
 
 unique{T}(A::NullableCategoricalArray{T}) = _unique(NullableArray{T}, A.refs, A.pool)
+
+function in{T, N, R}(x::Nullable, y::NullableCategoricalArray{T, N, R})
+    ref = get(y.pool, get(x), zero(R))
+    ref != 0 ? ref in y.refs : false
+end
+
+function in{S<:CategoricalValue, T, N, R}(x::Nullable{S}, y::NullableCategoricalArray{T, N, R})
+    v = get(x)
+    if v.pool === y.pool
+        return v.level in y.refs
+    else
+        ref = get(y.pool, index(v.pool)[v.level], zero(R))
+        return ref != 0 ? ref in y.refs : false
+    end
+end
+
+in{T, N, R}(x::Any, y::NullableCategoricalArray{T, N, R}) = false
+in{T, N, R}(x::CategoricalValue, y::NullableCategoricalArray{T, N, R}) = false
diff --git a/src/pool.jl b/src/pool.jl
index 52d03d9a..6aa246d5 100644
--- a/src/pool.jl
+++ b/src/pool.jl
@@ -86,6 +86,7 @@ Base.length(pool::CategoricalPool) = length(pool.index)
 
 Base.getindex(pool::CategoricalPool, i::Integer) = pool.valindex[i]
 Base.get(pool::CategoricalPool, level::Any) = pool.invindex[level]
+Base.get(pool::CategoricalPool, level::Any, default::Any) = get(pool.invindex, level, default)
 
 function Base.get!{T, R, V}(pool::CategoricalPool{T, R, V}, level)
     get!(pool.invindex, level) do
diff --git a/src/value.jl b/src/value.jl
index 1981f300..b80e5024 100644
--- a/src/value.jl
+++ b/src/value.jl
@@ -62,6 +62,9 @@ end
 Base.isequal(x::CategoricalValue, y::Any) = isequal(index(x.pool)[x.level], y)
 Base.isequal(x::Any, y::CategoricalValue) = isequal(y, x)
 
+Base.in(x::CategoricalValue, y::Any) = index(x.pool)[x.level] in y
+Base.in{T<:Integer}(x::CategoricalValue, y::Range{T}) = index(x.pool)[x.level] in y
+
 Base.hash(x::CategoricalValue, h::UInt) = hash(index(x.pool)[x.level], h)
 
 function Base.isless{S, T}(x::CategoricalValue{S}, y::CategoricalValue{T})
diff --git a/test/08_equality.jl b/test/08_equality.jl
index 0438a64a..3b7d7423 100644
--- a/test/08_equality.jl
+++ b/test/08_equality.jl
@@ -142,4 +142,13 @@ module TestEquality
     @test (ov2b == nv2a) === false
     @test (ov2b == nv1b) === false
     @test (ov2b == nv2b) === true
+
+    # Check in()
+    pool = CategoricalPool([5, 1, 3])
+    nv = CategoricalValue(2, pool)
+
+    @test (nv in 1:3) === true
+    @test (nv in [1, 2, 3]) === true
+    @test (nv in 2:3) === false
+    @test (nv in [2, 3]) === false
 end
diff --git a/test/13_arraycommon.jl b/test/13_arraycommon.jl
index 6c438698..fe116152 100644
--- a/test/13_arraycommon.jl
+++ b/test/13_arraycommon.jl
@@ -443,4 +443,29 @@ x = NullableCategoricalArray(1)
 @test_throws NullException CategoricalArray(x)
 @test_throws NullException convert(CategoricalArray, x)
 
+
+# Test in()
+ca1 = CategoricalArray([1, 2, 3])
+ca2 = CategoricalArray([4, 3, 2])
+
+@test (ca1[1] in ca1) === true
+@test (ca2[2] in ca1) === true
+@test (ca2[1] in ca1) === false
+
+@test (1 in ca1) === true
+@test (5 in ca1) === false
+
+nca1 = NullableCategoricalArray([1, 2, 3])
+nca2 = NullableCategoricalArray([4, 3, 2])
+
+@test (ca1[1] in nca1) === false
+@test (1 in nca1) === false
+
+@test (nca1[1] in nca1) === true
+@test (nca2[2] in nca1) === true
+@test (nca2[1] in nca1) === false
+
+@test (Nullable(1) in nca1) === true
+@test (Nullable(5) in nca1) === false
+
 end