A year-long follow-up of 1,742 patients treated for bipolar disorder demonstrated that rapid cycling, defined as four or more mood episodes per year, was rare but that 27% of the patients had “frequent cycling,” i.e., two or three episodes. In the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD), two-thirds of the patients had one or more episodes in the follow-up year. Patients with previous rapid cycling were more likely to have rapid cycling during follow-up, and Schneck et al. (CME, p. 370) report that rapid cycling was also associated with greater baseline clinical severity. Antidepressant use was consistently associated with more frequent cycling, but gender, bipolar subtype, and age at illness onset were not significant when other factors were considered. An editorial by Nassir Ghaemi on p. 300 focuses on antidepressant use for bipolar disorder.