Depressive syndrome was investigated in 132 psychiatric and neurologic patients by Zung's self-rating depression scale. The dexamethasone suppression test (DST) was carried out in 62 patients. Visual evoked potentials (VEP) (stimulation with flash (F-VEP) and pattern (P-VEP)), serum levels of LH, FSH, prolactin, ACTH, estradiol and cortisol were measured in 15 female patients between 85 and 94 years of age. Abnormal DST results indicated depression rather than dementia. P-VEP latencies correlated with cognitive symptoms, while F-VEP latencies correlated with affective symptoms. Gonadotropin levels were lowered in senility in comparison with the climacteric period of life. Depressive, anxious, cognitive, anorexic, sexual and disturbed diurnal mood changes syndromes could be separated by factor analysis. The severity of the cognitive depressive syndrome correlated negatively with estradiol serum levels. The total scores of Zung's self-rating depression scales correlated positively with ACTH and negatively with FSH serum levels.