There is compelling evidence that patients with schizophrenia are prone to gain weight. In addition, atypical antipsychotic (AAP) drugs also induce weight gain. All antipsychotic drugs produce weight gain but the potential varies. Many studies overwhelmingly confirm that AAP drugs produce substantially more weight gain in comparison to conventional antipsychotic drugs. Clozapine and olanzapine have the most weight inducing potential. Even ziprasidone, which is considered to be weight neutral, and aripiprazole a dopamine modulator produce weight gain in some. The pathophysiology of weight gain is complicated. Many neurohormones, neuropeptides, gut hormones, as well as adipose tissue and hair root derived hormones interact with environmental factors to produce weight gain. Management of weight gain is a difficult problem. Basic to treatment is an understanding of the etiology. Drug induced obesity provides a unique opportunity to psychiatrists to understand this clinically important problem. In the absence of this knowledge, prevention is the best hope. Education, diet control and simple behavioral measures may prevent excessive weight gain. In those with weight gain, treatment can be attempted with pharmacotherapy with careful monitoring of the side effects.