Introduction: Considering the importance of demographic and epidemiological characteristics of patients with bipolar disorder in the course and prognosis of this disorder, this study was conducted to investigate the relationship between clinical features of bipolar I patients in a manic phase with demographic and some epidemiological features.

Method: One hundred inpatients (65 men, 35 women) in a manic phase were selected using Con- venience Sampling. Diagnosis was made by means of clinical interview based on DSM-IV-TR criteria for diagnosis. The severity of illness was determined by hospitalization days and General Assessment of Functioning (GAF) scores. Data were analyzed using descriptive statistics, ana- lysis of variance and t-test.

Results: This study showed that the mean duration of hospitalization was higher for women (44.7 days) than for men (33.5 days). Also, there was a reverse correlation between GAF score and the number of hospitalization days.

Conclusion: The mean duration of hospitalization was higher for women in comparison with men. The lower the GAF score at the time of admission, the higher the number of hospitalization days.