The specific aim of this study is to evaluate the efficacy of levetiracetam 3 grams/day in modifying cocaine-using behavior, reducing cocaine craving and attenuating cocaine's reinforcing effect among methadone-maintained patients. The primary outcomes will be reduction in cocaine use as assessed by self-report and thrice-weekly urinalyses. Secondary outcomes will include weeks in treatment (retention) and change in measures of cocaine craving, anxiety symptoms and opiate withdrawal symptoms.