A total of 206 depressive patients (176 outpatients and 30 inpatients) underwent a dexamethasone suppression test (DST). Resting levels of serum growth hormone (GH), plasma vasopressin (AVP) and plasma homovanillic acid (HVA) were also measured in a proportion of the patients. Fifty-seven per cent of the endogenous patients showed nonsuppression of cortisol in the DST, while 92% in the nonendogenous group showed normal suppression. The diagnostic confidence of a positive test was 83%. The sensitivity and specificity of the test was slightly higher among inpatients than out-patients, and serum cortisol value at 4 p.m. was more useful than the morning value. No significant correlation was found between severity of the depression as measured by the Hamilton Rating Scale for Depression and serum cortisol. In single subjects there was, however, an obvious correlation. The levels of serum GH, plasma AVP and plasma HVA did not differ in the endogenous and nonendogenous groups, and there was no correlation between serum cortisol in the DST and the concentrations of the other hormones or HVA in plasma.