There are few publications about sexual impulse and sexual acts, related to sexuality in bipolar disorder (BPD) except from hypersexuality. There have been rare reports of paraphilia and transsexuality associated with BPD in literature. This association is commonly evaluated as comorbidity and handled as a curable sign of BPD, because of good response to mood stabilizers. In this paper we presented two cases that had transsexual acts only during manic episodes. Both patients dropped their behaviour after antimanic treatment and regretted what they had done. Therefore we have evaluated transsexual acts of these patients in BPD symptomatology and tried to explain these activities by biologic and psychodynamic basis.