diff --git a/src/FixedSizeArrays.jl b/src/FixedSizeArrays.jl
index 44d97b1..2868c4c 100644
--- a/src/FixedSizeArrays.jl
+++ b/src/FixedSizeArrays.jl
@@ -1,6 +1,7 @@
 module FixedSizeArrays
 
 include("FixedSizeArray.jl")
+include("FixedSizeBitArray.jl")
 
 if isdefined(Base, :dataids) && (Base.dataids isa Function)
     # This is an internal, non-public function which is nevertheless needed to
diff --git a/src/FixedSizeBitArray.jl b/src/FixedSizeBitArray.jl
new file mode 100644
index 0000000..4eaae6e
--- /dev/null
+++ b/src/FixedSizeBitArray.jl
@@ -0,0 +1,78 @@
+#unlike Base.BitArray, each column gets it's own chunk.
+function num_bit_chunks(size::NTuple{N,Int}) where {N}
+    prod(size[1:end-1]) * ((size[end]+63) >> 6)
+end
+
+struct FixedSizeBitArray{N} <: AbstractArray{Bool,N}
+    chunks::Memory{UInt64}
+    size::NTuple{N,Int}
+
+    function FixedSizeBitArray{N}(::Internal, size::NTuple{N,Int}) where {N}
+        nc = num_bit_chunks(size)
+        chunks = Memory{UInt64}(undef, nc)
+        # we want the last chunks to be zeroed and it's easier to just zero all of them
+        copyto!(chunks, UInt64(0))
+        new{N}(chunks, size)
+    end
+end
+
+const FixedSizeBitVector = FixedSizeBitArray{1}
+const FixedSizeBitMatrix = FixedSizeBitArray{2}
+
+
+function FixedSizeBitArray{N}(::UndefInitializer, size::NTuple{N,Int}) where {N}
+    checked_dims(size)
+    FixedSizeBitArray{N}(Internal(), size)
+end
+function FixedSizeBitArray{N}(::UndefInitializer, size::NTuple{N,Integer}) where {N}
+    size = map(Int, size)::NTuple{N,Int}  # prevent infinite recursion
+    FixedSizeBitArray{N}(undef, size)
+end
+function FixedSizeBitArray{N}(::UndefInitializer, size::Vararg{Integer,N}) where {N}
+    FixedSizeBitArray{N}(undef, size)
+end
+function FixedSizeBitArray(::UndefInitializer, size::NTuple{N,Integer}) where {N}
+    FixedSizeBitArray{N}(undef, size)
+end
+function FixedSizeBitArray(::UndefInitializer, size::Vararg{Integer,N}) where {N}
+    FixedSizeBitArray{N}(undef, size)
+end
+
+Base.IndexStyle(::Type{<:FixedSizeBitArray}) = IndexCartesian()
+
+function get_chunks_id(inds::NTuple{N,Int}) where {N}
+    prod(inds[1:end-1])+(inds[end] >> 6), inds[end] & 63
+end
+
+Base.@propagate_inbounds function Base.getindex(A::FixedSizeBitArray{N}, inds::Vararg{Int, N}) where {N}
+    @boundscheck checkbounds(A, inds...)
+    i1, i2 = get_chunks_id(inds)
+    u = UInt64(1) << i2
+    @inbounds r = (A.chunks[i1] & u) != 0
+    return r
+
+end
+Base.@propagate_inbounds Base.@assume_effects :noub_if_noinbounds function Base.setindex!(A::FixedSizeBitArray{N}, x, inds::Vararg{Int, N}) where {N}
+    @boundscheck checkbounds(A, inds...)
+    i1, i2 = get_chunks_id(inds)
+    u = UInt64(1) << i2
+    @inbounds begin
+        c = A.chunks[i1]
+        A.chunks[i1] = ifelse(x, c | u, c & ~u)
+    end
+    return A
+end
+
+Base.size(a::FixedSizeBitArray) = a.size
+Base.isassigned(a::FixedSizeBitArray, i::Int) = 1 <= i <= length(a)
+function Base.fill!(B::FixedSizeBitArray, x)
+    y = convert(Bool, x)::Bool
+    fill!(B.chunks, UInt64(0)-y)
+    # TODO zero partially filled chunks
+    return B
+end
+
+function Base.:(==)(A::FixedSizeBitArray, B::FixedSizeBitArray)
+    size(A) != size(B) && return false
+    return A.chunks == B.chunks
+end