Objectives: In this article, we review the evidence for, and implications of, a high rate of comorbid posttraumatic stress disorder (PTSD) in individuals with bipolar disorder. Methods: We reviewed studies providing comorbidity data on patients with bipolar disorder, and also examined the PTSD literature for risk factors and empirically supported treatment options for PTSD. Results: Studies of bipolar patients have documented elevated rates of PTSD. Based on our review, representing 1214 bipolar patients, the mean prevalence of PTSD in bipolar patients is 16.0% (95% CI: 14-18%), a rate that is roughly double the lifetime prevalence for PTSD in the general population. Risk factors for PTSD that are also characteristic of bipolar samples include the presence of multiple axis I disorders, greater trauma exposure, elevated neuroticism and lower extraversion, and lower social support and socio-economic status. Conclusions: These findings are discussed in relation to the cost of PTSD symptoms to the course of bipolar disorder. Pharmacological and cognitive-behavioral treatment options are reviewed, with discussion of modifications to current cognitive-behavioral protocols for addressing PTSD in individuals at risk for mood episodes.