To assess whether the anesthetic and anticonvulsant activities of alphaxalone display diurnal variability, groups of Syrian hamsters were studied at 4 h-intervals during a 24 h-cycle. The administration of alphaxalone (5 mg/kg) brought about a greater anesthetic activity (loss of righting reflex) at the middle of the photophase. When assessed in hamsters injected with 3-mercaptopropionic acid, alphaxalone displayed maximal anticonvulsant activity at the 4th of darkness. Evaluation of the time needed for first convulsive response indicated that alphaxalone did not show time-dependent effects, while in control hamsters seizure threshold was low during daylight and attained maximal values at night, showing a peak in seizure threshold at light-dark transition.