The authors examined the occurrence of traumatic brain injury (TBI) in individuals convicted of sexual offenses with and without bipolar disorder and a comparison group of patients with bipolar disorder without a history of sexual offending behaviors. Individuals convicted of sexual offenses and diagnosed with bipolar disorder had greater rates of brain injury resulting from head trauma than individuals convicted of sexual offenses without bipolar disorder and comparison patients with bipolar disorder. TBI predated the first sexual offense and/or the onset of bipolar disorder in most subjects.