In order to study the efficacy of estazolam versus triazolam in preoperative patients, two groups of 49 patients each were treated with 2 mg estazolam and 0.5 mg triazolam in a single dose, the night before surgery. This controlled study was designed to evaluate sleep patterns, emotional status on awakening and side effects, by the administration of a questionnaire either in the morning of the day before (baseline) or on the morning of surgery. The results show better sleep patterns after estazolam excepting the duration of sleep that was the same for the two drugs. The better emotional status upon awakening in the morning before surgery and the lower incidence of side effects in the patients treated with estazolam, lead to the conclusion that estazolam is clearly better than triazolam in the treatment of preoperative patients.