Depressive symptoms are a frequent component of schizophrenia and other psychotic illnesses. The treatment of psychoses with conventional (typical) antipsychotic agents may worsen depressive symptoms and many patients only partially respond to treatment. Typical antipsychotics are also associated with serious side effects, such as extrapyramidal symptoms, and sexual and menstrual dysfunction. Many of these pitfalls, however, can be avoided with atypical antipsychotics. Quetiapine, an atypical antipsychotic with proven efficacy in the treatment of psychotic symptoms in schizophrenia, also has efficacy for treating depressive symptoms in patients with schizophrenia and other psychiatric disorders. This suggests that quetiapine may also be effective in treating and preventing depressive symptoms in patients with affective disorders, such as bipolar disorder. A review of the evidence base supports the hypothesis that quetiapine does not cause treatment-emergent depression and may even be useful in the treatment and prevention of depressive symptoms in patients with bipolar disorder.