INTRODUCTION: Quetiapine (Seroquel(TM)) is an atypical antipsychotic drug with demonstrated efficacy and tolerability. In particular, placebo-level extrapyramidal symptoms (EPS) across the entire dose range and a low propensity to cause sexual dysfunction suggest it,nay be associated with greater patient acceptability than alternative treatments,. However,er, other side-effects, such as weight gain, may also have a significant impact on treatment acceptability. METHOD: We report the long-term weight changes observed in a cohort of 427 patients with schizophrenia from controlled and open-label extension (OLE) trials, in which quetiapine (mean dose 475 mg/day after 1 year) was the only antipsychotic medication during the OLE period. RESULTS: In these patients, there was no overall effect on weight across the body mass index (BMI) spectrum. There were no nose-related effects on weight, and only one patient withdrew front treatment due to an adverse event of weight gain. Quetiapine appeared to have a weight-neutral or 'normalizing' effect, with a tendency towards favourable shifts in bodyweight in underweight patients (BMI<18.5 kg/m(2)) and severely obese patients (BMI<greater than or equal to>35 kg/m(2)). CONCLUSION: These results indicate that long-term weight changes with quetiapine monotherapy are minimal and potentially beneficial, and do not appear to raise the medical concerns associated with some other atypical agents.