At discharge, a significantly larger percentage of unipolar patients treated with electroconvulsive therapy (ECT) respond with marked improvement as compared with those receiving antidepressants or other treatment. No treatment appears to be more efficacious in the bipolar group. In studying the covariables related to the length of time between hospitalizations, we found that the type of treatment is not important for the unipolar patient, whereas a combination of ECT and antidepressants lengthens the time to rehospitalization of the bipolar patient. Previous hospitalization is an important predictor variable for all patients.