Twenty-two Korean inpatients with delirium were administered prospectively a flexible dose of quetiapine. The delirium rating scale-revised-severity 98 (DRS-R-98) and clinical global impression scale-severity (CGI-s) scores were assessed at the time of pre- and post-treatment. The DRS-R-98 and CGI-s scores were significantly reduced by 57.3% and 55.1%, respectively. Quetiapine was effective and safe for the treatment of patients with delirium, and could be a useful alternative agent to classical antipsychotics in the treatment of delirium. Copyright © 2004 John Wiley & Sons, Ltd.