In recent years, poststroke depression has attracted worldwide interest. This review focuses on the major research themes that have emerged. Pooled data from studies conducted throughout the world have found prevalence rates for major depression of 19.3% among hospitalized patients and 23.3% among outpatient samples. The diagnosis of poststroke depression is most appropriately based on a structured mental state exam and DSM-IV criteria for depression due to stroke with major depressive-like episode or depressive features. Rarely, poststroke patients may also develop bipolar mood disorder. The treatment of poststroke depression has been examined in several placebo-controlled randomized clinical trials with both nortriptyline and citalopram showing efficacy. The progression of recovery following stroke can be altered by treating depression, which has been shown to improve recovery in activities of daily living and cognitive impairment and to decrease mortality. In addition, two studies have demonstrated that poststroke depression can be prevented using antidepressant medication, which also decreases the frequency of associated physical illness. Furthermore, two studies have shown that premorbid depression can significantly increase the risk of stroke over the subsequent 10-15 years. The mechanisms underlying the association of cerebrovascular diseases and mood disorder are important areas for future investigation.