  We propose an all-electrical nanoscopic structure where {\em pure} spin
current is induced in the transverse voltage probes attached to {\em
quantum-coherent} one-dimensional ring when conventional unpolarized charge
current is injected through its longitudinal leads. Tuning of the Rashba
spin-orbit coupling in semiconductor heterostructure hosting the ring generates
quasi-periodic oscillations of the predicted spin Hall current due to {\em
spin-sensitive quantum-interference effects} caused by the difference in
Aharonov-Casher phase acquired by opposite spins states traveling clockwise and
counterclockwise. Its amplitude is comparable to the mesoscopic spin Hall
current predicted for finite-size two-dimensional electron gases, while it gets
reduced in wide two-dimensional or disordered rings.
