Despite the many behavioral and cognitive treatment therapies that exist for cocaine addiction, individuals who complete cocaine abuse treatment are still at high risk for relapsing. Aripiprazole, a medication that is currently used to treat schizophrenia, may be useful in preventing drug relapse in individuals addicted to cocaine. This three-part study will evaluate the interaction between aripiprazole and cocaine. It will also determine the safety and effectiveness of aripiprazole in preventing drug relapse among cocaine addicts.