The present experiment sought to determine in rats if 1) tolerance develops to the amnesic effect of diazepam after chronic treatment, 2) the sedative and amnesic effects of diazepam can be dissociated via differential rates of tolerance development, and 3) withdrawal from long-term diazepam treatment affects mnemonic processes. Rats were given diazepam (3 mg/kg) acutely or chronically for 5, 15, or 30 d prior to behavioral testing. Sedation was assessed as exploratory activity in an open field and amnesia was assessed as spatial learning in the Morris water maze. Tolerance to the sedative effect of diazepam was exhibited after 5 d pretreatment whereas tolerance to the amnesic effect of diazepam was exhibited only after 30 d pretreatment. Withdrawal from diazepam produced a transitory and mild disruption of spatial learning. The data demonstrate 1) tolerance can develop to the amnesic effect of diazepam with extended treatment, 2) the sedative and amnesic effects of diazepam are largely independent, and 3) withdrawal from chronic diazepam treatment can retard optimal learning.