Quetiapine was developed in 1985 by scientists at AstraZeneca (formerly Zeneca) Pharmaceuticals. It received offi cial US Food and Drug Administration approval in September 1997 and approval in Germany in 2000. Since then, quetiapine has been used in the treatment of severe mental illness in approximately 70 countries including Canada, most Western European countries, and Japan. Quetiapine is a dibenzothiazepine derivative with a relatively broad receptor binding profi le. It has major affi nity to cerebral serotonergic (5HT 2A ), histaminergic (H1), and dopaminergic D 1 and D 2 receptors, moderate affi nity to α 1 -und α 2 -adrenergic receptors, and minor affi nity to muscarinergic M1 receptors; it demonstrates a substantial selectivity for the limbic system. This receptor occupancy profi le with relatively higher affi nity for the 5HT 2A receptor compared with the D 2 receptor is in part responsible for the antipsychotic characteristics and low incidence of extrapyramidal side-effects of quetiapine. The effi cacy of quetiapine in reducing positive and negative symptoms of schizophrenia has been proven in several clinical trials with placebo-controlled comparators. Quetiapine has also demonstrated robust effi cacy for treatment of cognitive, anxious-depressive, and aggressive symptoms in schizophrenia. Long-term trials show sustained tolerability for a broad spectrum of symptoms. Quetiapine has also proven effi cacy and tolerability in the treatment of moderate to severe manic episodes, and in the treatment of juveniles with oppositional-defi ant or conduct disorders, and in the geriatric dementia population. Recent data indicate that quetiapine may also be effective in the treatment of bipolar depressive symptoms without increasing the risk of triggering manic episodes, and in borderline personality disorder. In comparison with other antipsychotics, quetiapine has a favorable side-effect profi le. In clinical trials only small insignifi cant prolongations of the QT interval were observed. Weight-gain liabilities and new-onset metabolic side-effects occupy a middle-ground among newer antipsychotics. As a result of its good effi cacy and tolerability profi le quetiapine has become well established in the treatment of schizophrenia and manic episodes.