The dephasing dynamics of the continuum states has been investigated in bulk CdSxSe1−xmixed crystals with two‐ and three‐beam four‐wave mixing experiments using 10 fs pulses. Decay times, varying between 17 and 4 fs as a function of the density of electron‐hole pairs (8×1016–1018cm−3), indicate efficient Coulomb scattering with reduced screening as compared to bulk GaAs. Oscillations with 18 fs period which disappear within a few tens of femtoseconds are attributed to intervalence band quantum beats damped by intraband carrier thermalization. ©1995 American Institute of Physics.