  We show that the propagation of spin polarized carriers may be dramatically
affected by {\em inhomogeneous} electric fields. Surprisingly, the spin
diffusion length is found to strongly depend on the sign and magnitude of
electric field \emph{gradients}, in addition to the previously reported
dependence on the sign and magnitude of the electric field [Yu & Flatt\'e,
Phys. Rev. B {\bf 66}, 201202(R) 2002; {\em ibid.} {\bf 66}, 235302 (2002)].
This indicates that purely electrical effects may play a crucial role in spin
polarized injection, transport and detection in semiconductor spintronics. A
generalized drift-diffusion equation that describes our findings is derived and
verified by numerical calculations using the Boltzmann transport equation.
