The effects of oxazepam and diazepam (both at 10 mg/kg, i.p.) during continuous treatment for 15 days and following discontinuation after 5 days onwards on cerebral glutamic acid decarboxylase (GAD) and GABA-aminotransferase (GABA-T) have been studied. It has been found that during continuous treatment as well as following discontinuation after 5 days, a significant increase in GAD activity is observed in case of diazepam but not in case of oxazepam. On the other hand, a marked decrease in GABA-T activity is observed during continuous treatment up to 15 days with both diazepam and oxazepam but during discontinuation phase, the decreased GABA-T activity tends to increase and attain normal value much earlier in case of oxazepam than diazepam. This differential effect of oxazepam and diazepam on ?-aminobutyric acid (GABA) metabolism, following discontinuation of treatment, may possibly contribute to the difference in withdrawal effects associated with the two benzodiazepines.