This multicentre, observational, prospective, nonrandomized study compared the effectiveness and tolerability of quetiapine and risperidone in the acute and long-term treatment of schizophrenia in a clinical setting. Patients admitted to an acute unit with schizophrenia, schizophreniform or schizoaffective disorder (DSM-IV), who were prescribed quetiapine or risperidone (3 : 1 ratio) within the first week of treatment, according to the physician's usual practice, were recruited. In total, 492 patients (quetiapine: 367; risperidone: 125) were followed up at weeks 1 and 2, discharge and 6 and 12 months thereafter. Mean doses at 12 months were: quetiapine 718.5 mg/day and risperidone 7.0 mg/day. Efficacy measures (Brief Psychiatric Rating Scale, Clinical Global Impression Severity of Illness and Improvement) indicated similar results for both agents. No difference was found in rehospitalization rate with either drug. In terms of tolerability, orthostatic hypotension was more frequent with quetiapine, but extrapyramidal symptoms and male sexual dysfunction were more frequent with risperidone. In conclusion, quetiapine and risperidone had comparable effectiveness, but there were differences between treatments in their side effect profile.