Numerous studies have reported low melatonin secretion in depression, but other studies have suggested no deficit or an increase. Alterations of circadian phase or duration of melatonin secretion have also been described. Since melatonin secretion decreases as we age, it seemed interesting to examine melatonin and depression in an aging sample. Volunteers who complained of mood or sleep problems were recruited for studies in which fractional urine specimens were collected for 24 h, both at home and in the laboratory. The major metabolite, 6-sulfatoxymelatonin (aMT6s), was determined by radioimmunoassay. Of 72 volunteers aged 60-78 years, seven had current major depression and 55% had a lifetime history of an affective disorder. A 55-fold range of home aMT6s excretion rates was observed. A lifetime history of any affective disorder was significantly associated with greater log(10)[mesor] aMT6s excretion in home collections and laboratory collections, but current affective disorders were neither significantly related to melatonin excretion nor to aMT6s acrophase timing, onset, offset or duration. These results are only weakly consistent with a photoperiodic hypothesis of depression.