141 female psychiatric patients, suffering from major depression, schizophrenia, alcohol dependence or adjustment disorder, were investigated for their 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA) and cortisol level in the cerebrospinal fluid (CSF). Dexamethasone suppression tests were also performed in 111 cases, and TRH/TSH tests in 40 subjects. Fifty-two patients were hospitalized following a recent suicide attempt, 18 of which were made using a violent method. The other 34 attempters took tranquilizer or sedative overdoses. CSF 5-HIAA was significantly lower in violent attempters in all 4 diagnostic categories. CSF HVA was higher in those taking drug overdoses, but only in depression (and less markedly in schizophrenia). CSF cortisol did not differ among either diagnostic or suicidal subgroups. Dexamethasone suppression was more frequently abnormal in suicidal patients than in nonattempters, and this difference was more important where the overall nonsuppression rate was lower. Maximal TSH response to TRH showed an inverse correlation with CSF 5-HIAA, and it was lowest in the nonattempter group. The difference between violent suicide attempters and nonattempters in their TSH response was significant. Since these biochemical changes were more or less independent of clinical diagnoses, it seems relevant to explore further the biological background of human aggression and suicide as a separate research direction.