Obsessive-compulsive disorder (OCD) is one of the most common psychiatric disorders, occurring in 2% to 3% of the U.S. population. Borderline personality disorder is found in 2% of the U.S. population. These disorders denote the endpoints on a spectrum of compulsive and impulsive disorders. One endpoint marks compulsive or risk-aversive behaviors characterized by overestimation of the probability of future harm, highlighted by OCD. The other endpoint designates impulsive action characterized by the lack of complete consideration of the negative results of such behavior, such as borderline and antisocial personality disorders. This article examines studies testing the efficacy of different medications in treating compulsive and impulsive disorders. Mood stabilizers such as divalproex, selective serotonin reuptake inhibitors, monoamine oxidase inhibitors, and neuroleptics have documented efficacy in treating aggression and affective instability in impulsive patients.