The efficacy of zolpidem 20 mg was compared to that of flunitrazepam 2 mg. Forty-two insomniac female in-patients between 30 and 65 years of age were included in a double blind, parallel group trial and were randomly allocated to the two treatments. Study duration was 9 days with 2 days of placebo run-in, 5 days of active medication and 2 days of placebo withdrawal. Sleep latency, sleep duration, number of awakenings and time spent asleep during the night were given an ordinal score; condition in the morning was evaluated by Visual Analogue Scales and the psychomotor performance was evaluated by the tests: night-day for anterograde amnesia, digit span for verbal recall and Grünberger's fine motor function test. There was no significant difference between zolpidem and flunitrazepam for any of the variables; the drugs were significantly better than placebo baseline for all the sleep efficacy variables. The results of this study indicate that zolpidem is as effective as flunitrazepam in inducing and maintaining sleep but it does not induce a sense of weakness in the morning and does not impair memory.