We explored the course of bipolar I illness in 172 probands who were followed up prospectively for up to 5 years. Probands were grouped into three categories based on whether the symptoms of the index episode were only depressed, only manic, or mixed/cycling. Data were available for recovery from the index episode, subsequent relapse, and rates of recovery from the first prospective episode. Pure manic probands had a significantly faster rate of recovery (median, 6 weeks) than the mixed/cycling probands (median, 17 weeks), and the pure depressive probands had an intermediate rate (median, 11 weeks). After 5 years of follow-up the mixed/cycling patients continue to have the lowest cumulative probability of recovery from the index episode. Mixed/cycling probands also had a substantially faster time to relapse after recovery from the index episode compared with pure manic patients. For those patients who relapsed, the mixed/cycling patients had the lowest cumulative probability of recovery from the first prospectively observed episode. The treatment received by these patients is described and there is a discussion of how this treatment may have influenced the findings on course and outcome.