Sleep deprivation (SD) induces a rapid amelioration of mood in about 60 % of depressed patients. After the next night of sleep, however, most patients experience a relapse. Previous studies demonstrated that a six day sleep-phase advance protocol prevents relapses in about 60 % of patients who responded positively to SD. We investigated whether also a three day phase advance of the sleep period might be able to maintain the antidepressant effects of SD. Twenty-eight medicated depressed inpatients, who had a significant improvement after a SD in one night were recruited for this study. The phase advance protocol began on the first day after SD with a bed time from 5:00 p. m. to 12:00 p. m. on the first, from 7:00 p. m. to 2:00 a. m. on the second and 9:00 p. m. to 4:00 a. m. on the third day after SD. Three patients dropped out because of protocol violations. Only ten of the remaining 25 SD responders had a relapse during the three days of phase advance treatment or during the two days after it. Two of the relapsers improved again until day 6, i. e. 68 % showed an improvement of at least 30 % six days after the beginning of the treatment. This study indicates that even a three day phase advance protocol may help to prevent relapses after successful SD.