A detailed investigation of carrier relaxation in CdS0.5Se0.5, which has potential in ultrafast switching applications, has been carried out. It has been concluded from these investigations that there are three mechanisms for carrier relaxation in this material. At low 1.06‐&mgr;m radiation intensities the two‐photon‐induced photoconductivity decays slowly with a decay constant ?20 ms determined predominantly by bulk recombination of carriers. However, at high intensities this decay becomes very fast, with the recombination lifetime of the carriers estimated to be only a few nanoseconds. This drastic reduction in free‐carrier lifetime may be due to stimulated radiative recombination at high carrier densities. Single‐photon conductivity induced by low‐intensity 0.53‐&mgr;m radiation has been found to decay initially due to surface recombination of carriers.