The 24-hour excretions of adrenaline, noradrenaline, and 17-hydroxycortico-steroids were measured in normals and in a) acute and b) chronic schizophrenics, (c) non-schizophrenic psychotics, d) psychoneurotic disorders, and e) a miscellaneous group composed primarily of personality disorders. Some patients were studied over a period of time and the changes in hormone excretion and in clinical conditions compared. On comparison between groups, no difference was found in adrenaline and noradrenaline output. Similarly, when the patients were grouped by dominant emotional reaction at the time of test, no significant differences were observed. The acute schizophrenics, however, did show a greater output of free corticoids, but not of total corticoids compared to the normals. When the same patients were studied over a period of time, there appeared to be a relationship between catecholamine excretion and emotional tension and/or stages of illness. Depressed patients showed a decreased adrenaline and noradrenaline output on admission to hospital but only that of adrenaline was significant. Both adrenaline and noradrenaline showed a marked, but not significant decrease in acute schizophrenics after recovery. In the chronic schizophrenics, there was, after four months of withdrawal of tranquillizers, a significant rise in the output of both; the total and free corticoids showed a similar increase which, however, was not significant. Although no significant differences in hormone excretion were observed among the groups studied, other than increased excretion of free corticoids in the acute schizophrenics, the longitudinal studies in several groups suggest significant correlations may occur between changes in clinical condition and/or emotional state and the excretion of some of the hormones measured.