diff --git a/src/ForwardDiff.jl b/src/ForwardDiff.jl
index cfafe6a5..b697c5b7 100644
--- a/src/ForwardDiff.jl
+++ b/src/ForwardDiff.jl
@@ -18,6 +18,7 @@ include("derivative.jl")
 include("gradient.jl")
 include("jacobian.jl")
 include("hessian.jl")
+include("complex.jl")
 
 export DiffResults
 
diff --git a/src/complex.jl b/src/complex.jl
new file mode 100644
index 00000000..41551488
--- /dev/null
+++ b/src/complex.jl
@@ -0,0 +1,172 @@
+Base.prevfloat(x::Dual{T,V}) where {T,V<:AbstractFloat} = prevfloat(x.value)
+Base.nextfloat(x::Dual{T,V}) where {T,V<:AbstractFloat} = nextfloat(x.value)
+
+function Base.log(z::Complex{T}) where {A, T<:Dual{A,<:AbstractFloat}}
+    T1::T  = 1.25
+    T2::T  = 3
+    ln2::T = log(convert(T,2))  #0.6931471805599453
+    x, y = reim(z)
+    ρ, k = Base.ssqs(x,y)
+    ax = abs(x)
+    ay = abs(y)
+    if ax < ay
+        θ, β = ax, ay
+    else
+        θ, β = ay, ax
+    end
+    if k==0 && (0.5 < β*β) && (β <= T1 || ρ < T2)
+        ρρ = log1p((β-1)*(β+1)+θ*θ)/2
+    else
+        ρρ = log(ρ)/2 + k*ln2
+    end
+    Complex(ρρ, angle(z))
+end
+function Base.tanh(z::Complex{T}) where {A, T<:Dual{A,<:AbstractFloat}}
+    Ω = prevfloat(typemax(T))
+    ξ, η = reim(z)
+    if isnan(ξ) && η==0 return Complex(ξ, η) end
+    if 4*abs(ξ) > asinh(Ω) #Overflow?
+        Complex(copysign(one(T),ξ),
+                copysign(zero(T),η*(isfinite(η) ? sin(2*abs(η)) : one(η))))
+    else
+        t = tan(η)
+        β = 1+t*t #sec(η)^2
+        s = sinh(ξ)
+        ρ = sqrt(1 + s*s) #cosh(ξ)
+        if isinf(t)
+            Complex(ρ/s,1/t)
+        else
+            Complex(β*ρ*s,t)/(1+β*s*s)
+        end
+    end
+end
+
+_convert(T, x::Dual) = convert(T, x.value)
+function Base._cpow(z::Union{Dual{A,T}, Complex{<:Dual{A,T}}}, p::Union{Dual{B,T}, Complex{<:Dual{B,T}}}) where {T,A,B}
+    if isreal(p)
+        pᵣ = real(p)
+        if isinteger(pᵣ) && abs(pᵣ) < typemax(Int32)
+            # |p| < typemax(Int32) serves two purposes: it prevents overflow
+            # when converting p to Int, and it also turns out to be roughly
+            # the crossover point for exp(p*log(z)) or similar to be faster.
+            if iszero(pᵣ) # fix signs of imaginary part for z^0
+                zer = flipsign(copysign(zero(T),pᵣ), imag(z))
+                return Complex(one(T), zer)
+            end
+            ip = _convert(Int, pᵣ)
+            if isreal(z)
+                zᵣ = real(z)
+                if ip < 0
+                    iszero(z) && return Complex(T(NaN),T(NaN))
+                    re = Base.power_by_squaring(inv(zᵣ), -ip)
+                    im = -imag(z)
+                else
+                    re = Base.power_by_squaring(zᵣ, ip)
+                    im = imag(z)
+                end
+                # slightly tricky to get the correct sign of zero imag. part
+                return Complex(re, ifelse(iseven(ip) & signbit(zᵣ), -im, im))
+            else
+                return ip < 0 ? Base.power_by_squaring(inv(z), -ip) : Base.power_by_squaring(z, ip)
+            end
+        elseif isreal(z)
+            # (note: if both z and p are complex with ±0.0 imaginary parts,
+            #  the sign of the ±0.0 imaginary part of the result is ambiguous)
+            if iszero(real(z))
+                return pᵣ > 0 ? complex(z) : Complex(T(NaN),T(NaN)) # 0 or NaN+NaN*im
+            elseif real(z) > 0
+                return Complex(real(z)^pᵣ, z isa Real ? ifelse(real(z) < 1, -imag(p), imag(p)) : flipsign(imag(z), pᵣ))
+            else
+                zᵣ = real(z)
+                rᵖ = (-zᵣ)^pᵣ
+                if isfinite(pᵣ)
+                    # figuring out the sign of 0.0 when p is a complex number
+                    # with zero imaginary part and integer/2 real part could be
+                    # improved here, but it's not clear if it's worth it…
+                    return rᵖ * complex(cospi(pᵣ), flipsign(sinpi(pᵣ),imag(z)))
+                else
+                    iszero(rᵖ) && return zero(Complex{T}) # no way to get correct signs of 0.0
+                    return Complex(T(NaN),T(NaN)) # non-finite phase angle or NaN input
+                end
+            end
+        else
+            rᵖ = abs(z)^pᵣ
+            ϕ = pᵣ*angle(z)
+        end
+    elseif isreal(z)
+        iszero(z) && return real(p) > 0 ? complex(z) : Complex(T(NaN),T(NaN)) # 0 or NaN+NaN*im
+        zᵣ = real(z)
+        pᵣ, pᵢ = reim(p)
+        if zᵣ > 0
+            rᵖ = zᵣ^pᵣ
+            ϕ = pᵢ*log(zᵣ)
+        else
+            r = -zᵣ
+            θ = copysign(T(π),imag(z))
+            rᵖ = r^pᵣ * exp(-pᵢ*θ)
+            ϕ = pᵣ*θ + pᵢ*log(r)
+        end
+    else
+        pᵣ, pᵢ = reim(p)
+        r = abs(z)
+        θ = angle(z)
+        rᵖ = r^pᵣ * exp(-pᵢ*θ)
+        ϕ = pᵣ*θ + pᵢ*log(r)
+    end
+
+    if isfinite(ϕ)
+        return rᵖ * cis(ϕ)
+    else
+        iszero(rᵖ) && return zero(Complex{T}) # no way to get correct signs of 0.0
+        return Complex(T(NaN),T(NaN)) # non-finite phase angle or NaN input
+    end
+end
+
+function Base.ssqs(x::T, y::T) where T<:Dual
+    k::Int = 0
+    ρ = x*x + y*y
+    if !isfinite(ρ) && (isinf(x) || isinf(y))
+        ρ = convert(T, Inf)
+    elseif isinf(ρ) || (ρ==0 && (x!=0 || y!=0)) || ρ<nextfloat(zero(T))/(2*eps(T)^2)
+        m::T = max(abs(x), abs(y))
+        k = m==0 ? m : exponent(m)
+        xk, yk = ldexp(x,-k), ldexp(y,-k)
+        ρ = xk*xk + yk*yk
+    end
+    ρ, k
+end
+
+function Base.sqrt(z::Complex{T}) where {T<:Dual{<:Any,<:AbstractFloat}}
+    x, y = reim(z)
+    if x==y==0
+        return Complex(zero(x),y)
+    end
+    ρ, k::Int = Base.ssqs(x, y)
+    if isfinite(x) ρ=_ldexp(abs(x),-k)+sqrt(ρ) end
+    if isodd(k)
+        k = div(k-1,2)
+    else
+        k = div(k,2)-1
+        ρ += ρ
+    end
+    ρ = _ldexp(sqrt(ρ),k) #sqrt((abs(z)+abs(x))/2) without over/underflow
+    ξ = ρ
+    η = y
+    if ρ != 0
+        if isfinite(η) η=(η/ρ)/2 end
+        if x<0
+            ξ = abs(η)
+            η = copysign(ρ,y)
+        end
+    end
+    Complex(ξ,η)
+end
+
+# TODO: polish this ldexp function.
+function _ldexp(x::T, e::Integer) where T<:Dual
+    if e >=0
+        x * (1<<e)
+    else
+        x / (1<<-e)
+    end
+end
diff --git a/test/ComplexTest.jl b/test/ComplexTest.jl
new file mode 100644
index 00000000..f2cc438c
--- /dev/null
+++ b/test/ComplexTest.jl
@@ -0,0 +1,56 @@
+module ComplexTest
+using ForwardDiff: Dual
+using Test, ForwardDiff
+
+function numeric_jacobian_complex(f, args::T...; δ=1e-5, kwargs...) where T<:Complex
+    n = length(args)
+    J = zeros(2, 2n)
+    largs = [args...]
+    for i=1:n
+        # perturb real
+        largs[i] += δ/2
+        pos = f(largs...; kwargs...)
+        largs[i] -= δ
+        neg = f(largs...; kwargs...)
+        largs[i] += δ/2
+        J[1,2i-1] = (real(pos) - real(neg))/δ
+        J[2,2i-1] = (imag(pos) - imag(neg))/δ
+        # perturb real
+        largs[i] += δ/2*im
+        pos = f(largs...; kwargs...)
+        largs[i] -= δ*im
+        neg = f(largs...; kwargs...)
+        largs[i] += δ/2*im
+        J[1,2i] = (real(pos) - real(neg))/δ
+        J[2,2i] = (imag(pos) - imag(neg))/δ
+    end
+    return J
+end
+
+function complex_jacobian_wrapper(f)
+    function newf(params)
+        newargs = [Complex(params[2i-1], params[2i]) for i=1:length(params)÷2]
+        res = f(newargs...)
+        [real(res), imag(res)]
+    end
+end
+
+function check_complex_jacobian(f, args...; kwargs...)
+    nj = numeric_jacobian_complex(f, args...; δ=1e-5, kwargs...)
+    params = vcat([[x.re, x.im] for x in args]...)
+    fj = ForwardDiff.jacobian(complex_jacobian_wrapper(f), params)
+    @test isapprox(nj, fj, atol=1e-5)
+end
+
+@testset "complex instructions" begin
+    for OP in [+, *, /, -, ^]
+        println("  ...testing Complex Valued $OP")
+        check_complex_jacobian(OP, 4.0+2im, 2.0+1im)
+    end
+    for OP in [abs, abs2, real, imag, conj, adjoint, sin, cos, tan,
+            sinh, cosh, tanh, exp, log, angle, x->x^3, x->x^0.5, sqrt]
+        println("  ...testing Complex Valued $OP")
+        check_complex_jacobian(OP, 4.0+2im)
+    end
+end
+end
diff --git a/test/runtests.jl b/test/runtests.jl
index e19c9527..e610d0b0 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -31,3 +31,7 @@ println("done (took $t seconds).")
 println("Testing miscellaneous functionality...")
 t = @elapsed include("MiscTest.jl")
 println("done (took $t seconds).")
+
+println("Testing complex numbers...")
+t = @elapsed include("ComplexTest.jl")
+println("done (took $t seconds).")