Weight gain is a major side effect of treatment with clozapine and other antipsychotics. Recent studies suggest an important role of the serotonin type 2C receptor gene (5-HT2CR) in antipsychotic-induced weight gain. However, investigations pertaining to a possible association between a -759C/T polymorphism (C allele) of the 5-HT2CR and weight gain induced by clozapine and/or other antipsychotics have yielded inconsistent results. We investigated the -759C/T polymorphism of the 5-HT2CR in relation to clozapine-induced change in body mass index (BMI) (kg/m) in 97 German patients with schizophrenia and found no association between the -759C allele and weight gain after 12 weeks of clozapine treatment. In addition, confounding effects of initial BMI, age, sex and duration of illness on change in BMI could not be detected by multiple linear regression analysis. Our data do not support an involvement of the -759C/T polymorphism of the 5-HT2CR in clozapine-induced weight gain in German patients with schizophrenia. Further pharmacogenetic studies pertaining to antipsychotic-induced weight gain are warranted.