Recruitment for the Family Study of Cocaine Dependence (FSCD) targeted equal numbers of men and women, and equal numbers of European-American (EA) and African-American (AA) participants. Cocaine dependent subjects were recruited from inpatient and outpatient chemical dependency treatment centers in the St. Louis area. Eligibility requirements included meeting criteria for DSM-IV cocaine dependence, being 18 years of age or older, speaking fluent English, and having a full sibling within five years of age who was willing to participate in the family arm of the study. Control subjects were recruited through driver's license records maintained by the Missouri Family Registry, housed at Washington University School of Medicine for research purposes. Controls were matched to cocaine dependent subjects based on age, ethnicity, gender, and zip code. Exclusionary criteria for controls included dependence on alcohol or drugs, including nicotine. Controls were required to have at least used alcohol in their lifetime because substance-abstinent individuals are considered phenotypically unknown; i.e., they may have a high genetic liability for addiction, but the absence of any substance use would preclude their progression to dependence. Blood samples
