The temperature rhythms of 9 drug-free patients with primary affective disorder were measured during depression and after recovery and compared with those of 12 normal controls. The patients had higher nocturnal temperatures and decreased 24-hour amplitudes when depressed than when they had recovered and compared to the controls. There was no evidence that the temperature minimum occurred earlier in the night in depression compared to controls. However, in 4 of 7 patients the temperature minimum occurred earlier in the night during depression compared to recovery.