The use of anticonvulsants is expanding in the treatment of bipolar and related disorders. Although they have characteristics in common, the anticonvulsants currently used are quite diverse and vary in their spectrum of activity, quality of supporting evidence, and organ toxicities. Common side effects of anticonvulsants that can limit tolerability but are not physiologically severe include sedation and other cognitive impairments, tremor, and gastrointestinal side effects. Possibly less common, but of more physiologic significance, are effects on body weight and metabolism and dose-related hepatic and hematologic effects. Severe, but rare, toxicities include skin, bone marrow, and hepatic toxicity due to hypersensitivity. The most important aspect of successful management of severe toxicities is early detection, discontinuation of the medicine, and vigorous treatment of the toxicity. Anticonvulsants can also be associated with fetal toxicity, especially neural tube defects. In general, anticonvulsants are well tolerated and their effectiveness greatly outweighs risk or annoyance from side effects, but side effects must be kept in mind when choosing and monitoring treatment.