2. They are dependent on other substances except nicotine or cocaine at the time of participation. Use of other abused substances will be allowed as long as they are not currently dependent on any drug except nicotine and cocaine. Justification: Dependence on other substances may result in unique CNS deficits that would increase the noise in our data. Further, other dependence may contaminate neural processes examined. Nicotine dependence will be allowed since nicotine use is not associated with a drug high in normal usage and the prevalence of nicotine dependence in cocaine using individuals may make it impractical to exclude them. Assessment tool(s): Substance Use Disorders module of the SCID with confirmation by clinical interview and negative urine drug screen. Positive screens for cocaine are allowed.