Objective: There were two aims: first, to examine the relationship between prior sexual abuse and three types of adult risky sexual behaviors [(1) ever traded sex for drugs or money, (2) had unprotected sex in the past 6 months, and (3) frequency of unprotected sex in the past 6 months] among persons with severe mental illness (SMI), and second, to examine the potential mediating effects of adult rape, substance use, and PTSD. Method: Using a pooled sample of individuals with SMI (N=609), logistic and negative binomial regression analyses were used to investigate the impact of prior sexual abuse on these adult risky sexual behaviors. Results: Childhood sexual abuse was associated with having ever traded sex for money and having engaged in unprotected sex in the past 6 months. However, childhood sexual abuse was inversely associated with the number of times males had unprotected sex in the past 6 months. Results differed between males and females and the impact of potential mediators also varied by gender and type of outcome studied. Conclusion: These findings suggest a complex link between childhood sexual abuse and adult risky sexual behaviors in persons with SMI. Clinical assessments of child abuse sequelae should include a variety of indicators and parameters of adult risky sexual behavior, as persons with SMI are at an increased risk of engaging in high-risk sexual behaviors and tend to have a higher exposure to childhood sexual abuse than does the general population.