To assess the clinical validity of individual DSM-IV criteria for hypomania. In an international sample of 5,635 patients with major depressive episodes (Bridge Study), DSM-IV criteria for hypomania (stem questions, number and quality of symptoms, duration and exclusion criteria) were systematically assessed and their validity analysed on the basis of clinical data including family history, course, and other clinical characteristics. Three stem questions for hypomania, irritability, elevated mood and the added question of increased activity, showed comparable validity. The results support the current DSM-IV requirement for a higher symptom threshold (4 of 7 hypomanic symptoms) in cases of irritable mood. Longer durations of hypomanic episodes were associated with higher scores on all validators. The results did not support the DSM-IV durational requirements for hypomanic episodes (4 days) and manic episodes (7 days). Brief hypomanic episodes of 1, 2 or 3 days were valid and would meet validity criteria for inclusion. The three exclusion criteria in DSM-IV (hypomania due to the use of antidepressants or of other substances, or to other medical conditions) were found to exclude patients with bipolar depression and should therefore not be retained. These results support several revisions of the DSM-IV concept of hypomanic episodes: specifically, the inclusion of increased activity as a gate question, the inclusion of 1 or 2 to 3-day episodes and the elimination of all exclusion criteria.