Circadian disorganization was studied in 15 normal males. Following a 5 day baseline period, a 12 hour photoperiod shift took place followed by a 10 day recovery period. Analysis of data on a subject who suicided 2 weeks after the study indicated that he differed, rhythmically from the other subjects, suggesting that circadian asynchrony & an inability to respond effectively to phase shift may characterize a presuicidal state.(NBB)