Depressive mixed states (DMS) (major depressive episodes with some hypomanic symptoms) are understudied, and not classified in DSM-IV. The study aim was to find prevalence of DMS among depressed outpatients, to study clinical differences between DMS and non-DMS, and relationships of DMS with unipolar and bipolar II. Ninety eight consecutive DSM-IV bipolar II and unipolar depressed outpatients were interviewed with the Structured Clinical Interview for DSM-IV. DMS was defined as an MDE with at least two concurrent hypomanic symptoms. DMS was present in 62.2% of patients [48.7% of unipolar, 71.9% of bipolar II, (p=0.022)]. DMS had significantly fewer unipolar, more bipolar II patients, lower age at onset, and more atypical features than non-DMS. Bipolar II DMS had significantly more recurrences, more atypical features, and lower age at onset (trend) than unipolar DMS. Bipolar II DMS had (trend) lower age at onset and more atypical features than bipolar II non-DMS. High DMS prevalence has important treatment implications, as antidepressants may worsen DMS, and some antidepressant-resistant depressions may be DMS responding to mood stabilizers. DMS may be distinct from non-DMS, but not from unipolar and bipolar II disorders, and this distinction may be due mainly to high bipolar II prevalence in DMS.