The development of novel, atypical antipsychotics has been welcomed due to their lower incidence of extrapyramidal side effects. However, as with all pharmacotherapy, patient response is often varied and these novel compounds are not without their own side effect profile, most notably weight gain. Inter-individual variations in response to drug treatment are, in part, due to polymorphisms of the genes encoding drug targets. The importance of the serotonin system in psychiatric symptomatology and several side effects of antipsychotic drugs is well established. Thus genetic polymorphisms of two central 5-HT receptors (5-HT2A and 2C), at which many of the newer antipsychotic drugs act, are prime candidates for pharmacogenetic analysis of the effects of these drugs in the treatment of schizophrenia. To date, much work has focussed on the 5-HT2A receptor subtype. However, pharmacological evidence and recent molecular genetic studies would suggest a role for the 5-HT2C receptor in the consequences of antipsychotic treatment, particularly in relation to the development of both drug-induced dyskinesias and weight gain. This review briefly examines the pharmacology and physiology of the 5HT2C receptor in the context of its genetics, with discussion of known polymorphisms of this receptor gene and its promoter region. Associations between these polymorphisms and the development of schizophrenia, the symptom responses to antipsychotic treatment and side effects of such treatment, notably tardive dyskinesia and weight gain, are assessed and related to the presumed functionality of these polymorphisms. Such studies clearly demonstrate the potential of pharmacogenetics in optimising treatment for the individual patient.