A 77-item questionnaire on cocaine and "crack" use patterns, and on the addictive, medical, and criminal consequences of such use, was completed by 464 largely white, middle-class, suburban, teenage drug abusers registered in seven geographically disparate outpatient treatment facilities. Of the 130 (28%) who smoked crack, 87 (67%) were designated as "experimenters" (use of crack 1 to 9 times); 20 (15%) were in an intermediate group (smoked crack 10 to 50 times); and 23 (18%) were heavy users (smoked crack more than 50 times). Sixty percent of heavy users progressed from initiation of crack use to its use at least once a week in less than 3 months. Almost 50% of the 87 experimenters and nearly all the 23 heavy users recalled preoccupation with thoughts of crack, rapid loss of the ability to modulate their use of the drug, and rapid development of pharmacologic tolerance. Suspiciousness, mistrust, and depressed mood were associated with the increasing use of crack. Seizures occurred in none of those who used cocaine by snorting it intranasally (without ever smoking crack), in contrast to 1% of the experimenters and 9% of the 43 respondents who had smoked crack at least 10 times. Seven percent of the 87 experimenters versus almost one fourth of the 43 who smoked crack more frequently had had injected cocaine intravenously. The use of crack by middle-class adolescents is associated with rapid addiction and with serious behavioral and medical complications.