Objective: Literature indicates that rapid cycling (RC) feature in bipolar disorder (BD) has been associated with worse disorder outcome and more severe disability. We aimed to investigate factors that affect or involved in vulnerability to increase rapid cycling in the previous 12 months. Methods: This is a cross-sectional study. Patients (n=380) were recruited from an outpatients clinic of a general hospital. Diagnostic interviews were performed with Structured Clinical Interview for DSM-IV Disorders (SCID-I) and SCID-II. Sociodemographic Form, Young Mania Rating Scale (YMRS) and Hamilton Depression Rating Scale (HAM-D) were applied. RC was defined as presence four or more mood episodes in the previous 12 months. Patients were arranged as whether having rapid cycling bipolar disorder (RCBD) or not. RCBD was compared to the group of non-RCBD patients regarding the sociodemographic and clinical data. Results: Study group showed a female preponderance (65.0%). Sixty patients (15.8%) had RC in the previous 12 months. There were statistically significant differences between two groups regarding in number of suicide attempts, family history of mood disorders, psychotic depression, number of antidepressants utilized, manic, depressive, mixed and total number of episodes. Discussion: The presence of RC in the previous 12 months was found correlated with specific clinical features closely related to worse outcome in the course of BD. Further studies are needed to clarify disease-related factors in patient groups with a standard definition of homogeneous RCBD.