The incidence of hypomania/mania was studied in 203 consecutive mood disorder outpatients, presenting for treatment of depression in private practice, during a follow-up of 3 to 6 months. Of these 50.7% were unipolar, 45.3% were bipolar II, and 3.9% were bipolar I patients. Compared to unipolar patients, bipolar II patients had a threefold greater risk of switching (17.3% vs. 5.8%, a significant difference), but a lower rate than expected from previous work. In a previous analysis of the whole sample, bipolar II patients had a lower age at onset and more frequent atypical features than unipolar patients. Both unipolar and bipolar switchers had instead early age at onset and frequent atypical features, suggesting that these factors might increase the risk of switching in unipolar depression.