The object of this investigation was to study the effect of a benzodiazepine upon the cycle wakefulness-sleep. Wistar rats received 0.9 mg/kg of the chlorate derivative of beta lactam 1.5 benzodiazepine intraperitoneally and the action was analyzed by means of continuous polygraphic registers for ten hours long. Results indicate that this substance decreases wakefulness and slightly increases slow wave sleep. Paradoxical sleep increases significantly (p less than 0.05). Latency of the first phase of paradoxical sleep decreases considerably. These effects suggest that this compound favors sleep under present experimental conditions.