Cocaine dependent cases were recruited from alcohol and drug treatment centers, including publicly and privately funded inpatient and outpatient facilities in the city of St. Louis and surrounding counties in Missouri. Eligible cases met criteria for DSM-IV cocaine dependence, spoke fluent English, and were at least 18 years of age. Because this was initially designed as a family-based study, cocaine dependent cases were also required to have a full sibling within five years of their age who was willing to participate. To increase the number of complete sibling pairs, cocaine dependent cases were interviewed only after their siblings participated. Response rates were calculated among eligible participants only, which excludes individuals who did not have a sibling participate. Of the eligible cocaine dependent cases, 77.1% participated. Non-participation was due to inability to locate a subject after initial contact (58.7%), subject refusal (20.3%) and other miscellaneous reasons (21%).
