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Objective: To test the hypothesis that patients with bipolar disorder (BPD) differ demographically and clinically within subgroups based on the predominant-polarity of major recurrences., Method: We tested factors for association with predominantly (≥2 : 1) depressive vs. mania-like episodes with 928 DSM-IV type-I BPD subjects from five international sites., Results: Factors preliminarily associated with predominant-depression included: electroconvulsive treatment, longer latency-to-BPD diagnosis, first episode depressive or mixed, more suicide attempts, more Axis-II comorbidity, ever having mixed-states, ever married, and female sex. Predominant-mania was associated with: initial manic or psychotic episodes, more drug abuse, more education, and more family psychiatric history. Of the 47.3% of subjects without polarity-predominance, risks for all factors considered were intermediate. Expanding the definition of polarity-predominance to ≥51% added little, but shifting mixed-states to 'predominant-depression' increased risk of suicidal acts from 2.4- to 4.5-fold excess over predominant-mania-hypomania, and suicidal risk was associated continuously with increasing proportions of depressive or mixed episodes., Conclusion: Subtyping by predominant-polarity yielded predictive associations, including the polarity of first episodes and risk of suicide attempts. Such subtyping may contribute to improve planning of clinical care and to biological studies of BPD., (© 2011 John Wiley & Sons A/S.)