Observations made with quetiapine (QUET) in this case give clues for some aspects of its use for patients with bipolar disorder. Weight gain (11 kg; 16.6% increase in 21 weeks) and improvement in manic symptoms occurred after QUET add-on to lithium (Li). Patient's mood improved after QUET add-on without causing extrapyramidal symptoms (EPS), while QUET was discontinued due to weight gain. Shortterm QUET add-on to Li may help mood stabilization in bipolar I disorder. Weight changes must be observed carefully. (C) 2003 Elsevier Inc. All rights reserved.