We interviewed 219 patients with a questionnaire to evaluate the prevalence of insomnia, and to assess whether benzodiazepine therapy was correctly indicated. Insomnia was present in 86 patients (39%), being initial in more than one half. Thirty-two of the patients with insomnia were receiving benzodiazepines (37%), 24 of whom (75%) had been treated for more than one year. The drug was incorrectly indicated in 18 (56%), in most cases because it was inappropriate for the type of the patient's insomnia. In six of these patients (33%), incorrect indication was related with self-medication. The benzodiazepine was incorrectly indicated in all the patients with diurnal oversedation. We emphasize the frequency of incorrect indications of these drugs, and we insist on the need that general practitioners have of a better knowledge of the pharmacokinetics of each drug, which is the basis for a correct indication.