OBJECTIVE: The clinical experience of the authors has suggested there is a significant group of elderly and individuals with medical illness and depressive symptoms who do not meet DSM-IV criteria for major depression. We were interested in all available data regarding minor depression in both the medically ill and community individuals. METHODS: MEDLINE was searched from 1965 to 1995, using the terms "depressive disorders" and "medical illness," as well as "atypical depression" and "elderly." Relevant references from these primary articles were also utilized. RESULTS: In medical patients, depressive symptoms were associated with decreased likelihood of discharge to home. Although diagnostic criteria vary, some suggest anhedonia as the central feature. From 3 to 16 percent of medical outpatients suffer from minor depression. Up to 64 percent of medical inpatients will complain of depressed mood. Studies in community samples found that minor depression was responsible for 9 to 16 percent of total disability days, and was associated with absenteeism from work, as well as separation and divorce. Little is known about the natural history and prognosis of minor depression. CONCLUSIONS: Minor depression is both common and has a significant impact on the health care system, and therefore deserves further study.