Abstract This chapter focuses on a review of randomized clinical trials of both psychosocial and behavioral interventions designed to directly reduce rates of suicide and parasuicidal behavior, including suicide attempts. It begins with an overview of the definitional difficulties in this field and then proceeds to an overview of treatment issues and a comprehensive review of treatment studies aiming to reduce suicidal behavior among suicidal individuals. Twenty studies are discussed. Eighteen studies randomly assigned subjects to the experimental and control condition; the other two studies assigned subjects in an alternating sequential fashion. Analyses showed that four psychosocial intervention studies and one pharmacotherapy study have reported efficacious results when compared to treatments-as-usual or placebo controls. From another perspective, when outpatient psychosocial interventions were examined, the strongest predictor of whether the experimental treatment would be more effective than the control was whether high-risk suicidal individuals were included. Psychosocial interventions appear to be most effective with the more high-risk individuals.