Night sleep recordings were performed in 10 patients with sleep disturbance in falling asleep as well as in maintaining sleep using a mobile 4-channel EEG registration system. Three consecutive nights, which were spent under different conditions, were evaluated automatically. The first night without treatment was used as a baseline night to objectify the disturbed sleep, the second night was measured following an infusion of a physiological saline solution and prior to the third recording 5 g l-tryptophane were applied to the patients. Besides a significant decrease of delayed latency times until the appearance of the light sleep stages, an influence was seen on the quantitative sleep parameters such as sleep period time and total sleep time. In parallel, an improvement of the subjective feeling measured by a self-rating scale resulted after l-tryptophane. On the other hand, no definite influence on the other sleep parameters such as an increase of slow wave sleep was observed, so that the use of this treatment might be recommended in disturbances in falling asleep particularly.