Insomnia, a common complaint among the elderly, is generally treated with benzodiazepines. Long-acting benzodiazepines (e.g., flurazepam) often produce daytime somnolence and performance deficits, whereas short-acting drugs (e.g., triazolam) have been associated with marked rebound insomnia and anterograde memory loss. The authors designed a pilot study to evaluate the efficacy of an intermediate-acting benzodiazepine, estazolam (e.g., ProSom), as well as its side effects. The parameters studied were sleep, daytime performance, and memory. Ten geriatric patients (greater than 60 years of age) with insomnia participated in the study. They received placebo nightly for 2 weeks (baseline), estazolam 1 mg nightly for the next 4 weeks (treatment phase), and placebo again for 2 weeks (withdrawal period). Sleep was monitored by polysomnography the first two nights of each week in a sleep laboratory. Estazolam significantly decreased sleep latency, nocturnal awakenings, and wake time after sleep onset. Total sleep time increased an average of 63 minutes the first night of treatment. Significant improvements in wake time after sleep onset and total sleep time also were observed in the fourth week of estazolam treatment. Rebound insomnia occurred on the first withdrawal night only for wake time and total sleep time. By the next night, these sleep parameters returned to baseline. Neither day-time performance nor anterograde memory was adversely affected by estazolam treatment or its withdrawal. A 1-mg dose of estazolam appears to be a safe and effective hypnotic for elderly patients with insomnia.