Some clinical differences between gender regarding the course and outcome of bipolar disorders have already been described and some others remain still controversial.To explore gender differences regarding clinical and socio-demographic characteristics amongst bipolar patients with particular attention to predominant polarity and depressive symptoms.Data were collected from DSM-IV type I and II bipolar patients (n=604), resulting from the systematic follow-up of the Bipolar Disorders Program, Hospital Clinic of Barcelona, over an average follow-up of 10 years. Socio-demographic and clinical variables were collected in order to detect gender-related differences.Bipolar women are more likely than men to show a predominance of depressive polarity as well as a depressive onset whilst men would be more likely to suffer from comorbid substance use disorders. Women significantly have a higher lifetime prevalence of psychotic depression and a higher prevalence of axis II comorbid disorders. Bipolar women are also more likely to have a family history of suicide and a lifetime history of attempted suicide. Suicide attempts are more often violent amongst bipolar men. In a backward logistic regression model, two variables were responsible for most gender-related clinical differences: type of predominant polarity - more likely to be depressive amongst women - (B=-0.794, p=0.027, Exp(B)=0.452; CI= 0.223-0.915), alcohol abuse (B=-1.095, p=0.000, Exp(B)=2990; CI= 1.817-4.919) and cocaine abuse (B=0.784, p=0.033, Exp(B)=2.189; CI= 1.066-4.496) - more prevalent amongst men.The main characteristic featuring bipolar women is depression, both at illness onset and as a predominant polarity all along the illness course. This may have important diagnostic and therapeutic implications.