Onset, course, and outcome of affective disorders were studied prospectively – at 5-year intervals, until 1980 – in 406 patients admitted to the Psychiatric University Hospital, Zurich, between 1959 and 1963. A few results are summarized. Bipolar I and bipolar II disorders take a very similar course. The distinction between unipolar depression and bipolar affective disorder, and the separation by presence or absence of psychotic features (delusions and hallucinations), and then again by mood congruence, are of high prognostic value.