Recent interest in the role of serotonin (5-HT) in antipsychotic drug action is based mainly upon the fact that antipsychotic drugs such as clozapine, olanzapine, quetiapine, risperidone, sertindole, and ziprasidone are potent 5-HT2a receptor antagonists and relatively weaker dopamine D2 antagonists. These agents share in common low extrapyramidal side effects at clinically effective doses and possibly greater efficacy to reduce negative symptoms. As a group, they also have a superior effect on cognitive function and greater ability to treat mood symptoms in both patients with schizophrenia or affective disorders than typical antipsychotic drugs. The atypical antipsychotic agents vary in their affinities for other types of 5-HT as well as dopamine, muscarinic, adrenergic, and histaminic receptors, some, or all of which, may contribute to their differences in efficacy and side effect profile. Of the other 5-HT receptor which these drugs directly, the 5-HT1a and 5-HT2c receptors are the strongest candidates for contributing to their antipsychotic action and low EPS profile. The 5-HT6 and 5-HT7 receptors may also be of some importance. Stimulation of the 5-HT1a receptor appears to produce many of the same effects as antagonism of the 5-HT2a receptor while antagonism of the 5-HT2c receptor appears to diminish some of the actions of 5-HT2a receptor antagonism. Future antipsychotic drug development can include targeting multiple serotonin receptor subtypes.