Rapid cycling patients (greater than or equal to 4 episodes/year) often show inadequate response to lithium carbonate and are vulnerable to antidepressant-induced switches or cycle acceleration. Treatment with the anticonvulsant carbamazepine is now an accepted adjunct or alternative, and a series of uncontrolled studies also suggest the utility of valproate in this patient population. Clonazepam, suppressive doses of thyroid, calcium channel blockers, and other innovative treatments appear promising and deserve careful clinical investigation.