Free cortisol in urine, temperature and heart rate were examined in 81 endogenous depressives and 15 healthy controls in five successive 24-hour rhythms. The nocturnal mean value, amplitude, phase position of the minima and period length were calculated. Main results: cortisol secretion is to be found in larger quantities in depressives than in healthy controls. The amount of cortisol is again raised after a period of sleep deprivation and simultaneously the amplitude becomes larger. Temperature measurements revealed an enlargement of the amplitude following treatment with tricyclic antidepressants. A minimal increase in heart rate is evident in endogenous depressives in comparison with healthy subjects. The heart rate in the entire circadian course is significantly increased by antidepressants. All three variables showed a phase advance of the nocturnal minima in endogenous depression. Alterations in period length could not be detected. The findings were discussed in regard to chronobiological dissertations on endogenous depression.