Although depressive disorders in the elderly represent a major public health concern by virtue of their high cost in human suffering, disability, and potential suicide, they have not been studied extensively, and specific criteria for diagnostic classification and optimal treatment are lacking. It seems likely that many of the affective syndromes in the elderly like senile melancholia, manic depressive illness, pseudodementia, and masked depression belong to the group of endogenous depressions, and can be identified by a constellation of clinical symptoms (endogenous or endogenomorphic profile), abnormal dexamethasone suppression test (DST) (at least 50%), and positive response to treatment with antidepressant medication. The rest are depressions reactive to psychogenic or sociogenic factors frequently presenting agitation as a dominant symptom, and finally there is a group of organic depressions due to underlying organic brain change, (i.e. senile dementia). It is possible that careful psychometric and psychiatric evaluation based on the symptom pattern, DST, and response to treatment would reveal reliable differences between pseudodementia and mild dementia and distinguish endogenomorphic from non-endogenomorphic depressions, respectively. The validity of such an approach remains to be demonstrated. Biological research in this area has provided valuable findings and should be the aim for the 1980s.