Loprazolam is a benzodiazepine derivative which possesses, in animals, a potent hypnotic effect. In a double-blind single-dose study, three dose levels of loprazolam (0.5, 1.0, and 2.0 mg) were compared to each other as well as to 15 mg flurazepam and placebo in 60 insomniac outpatients. The 0.5- and 1.0-mg doses demonstrated hypnotic potency comparable to that of flurazepam, and all three treatments were superior to placebo. The hypnotic effect of the 2-mg dose of loprazolam was significantly greater than that of the other treatments, but at this dose, patients experienced significantly more side effects and morning hangover.