Despite the important contribution of lithium to the treatment of manic-depressive illness, its notable relapse and recurrence rates make the development of new therapies a high priority. The author presents data on the course of illness in bipolar I disorder patients whose index episodes reflected manic symptoms only, depressed symptoms only, or a combination, either mixed or cycling. The patients received different types of treatment. To be considered recovered, the patients either had to have been asymptomatic or had to have had only one or two symptoms of minimal severity for 8 consecutive weeks. The patients with purely manic index episodes recovered at a much faster rate than did those whose index episodes were mixed or cycling. The patients who were purely depressed at entry had intermediate courses. By 8 weeks, 61% of the pure manics were recovered, compared with 44% of the pure depressives and 33% of the mixed and cycling patients.