This study examined the prevalence of suicidal behaviors among 1,638 Northern Plains American Indians ages 15?57. Age and gender patterns were investigated as was comorbidity with psychiatric and substance use disorders. Data from a population-based survey indicated that suicidal behaviors were more frequently reported among females than males and among younger respondents than older respondents. In addition, suicidal behaviors were associated with depressive disorders, PTSD, substance abuse/dependence, and violent ideation/aggression. Results underscore the importance of effective and acceptable alcohol, drug, and mental health services in reducing the rates of suicidal behaviors in American Indian communities.