Weight gain has been observed with many of the antipsychotics, including the atypical antipsychotics. The assessment of whether, and to what degree, a drug causes changes in body weight is not straightforward, since clinical studies performed during a drug development program are not designed to measure changes in body weight. Even when weight change data are obtained from adverse event data or from part of the vital signs measured during a study, assessment is not standardized. Nevertheless, evidence points to the fact that weight gain with the atypical antipsychotics is becoming an increasing problem. This review examines whether antipsychotic-associated weight gain, when it occurs, is associated with clinical outcome parameters.