Pharmacotherapy of bipolar disorder is a rapidly evolving field. Mood stabilizers and anticonvulsants have varying biochemical profiles which may predispose them to different adverse effects and drug-drug interactions. Several of the new anticonvulsants appear less likely to have the problems with drug-drug interaction. To provide more effective combination pharmacotherapies, clinicians should be allowed to anticipate and avoid pharmacokinetic and pharmacodynamic drug-drug interactions. We reviewed the role of cytochrome P450 isozymes in the metabolism of the drugs and their interactions. The drug-drug interactions of several classes of drugs which used as mood stabilizers and new anticonvulsants, some of which may have psychotropic profiles, are discussed mainly in this article. Finally, potential pharmacokinetic interactions between the benzodiazepines and other coadministered drugs are discussed briefly.