Crack remains at the center of the cocaine epidemic in the city. About 72 percent of admissions to treatment with cocaine as the primary drug of abuse report smoking as the mode of administration. About 83 percent of arrests involving cocaine are actually crack-related. Treatment admissions with heroin as the primary drug of abuse have increased in 1990. The intranasal use of heroin continues to grow as a mode of administration. Although marijuana continues to be the most widely used illicit substance, indicators of marijuana abuse are declining. Hospital emergencies and treatment admissions indicate that the nonmedical use of psychoactive prescription drugs is becoming less of a serious problem. Treatment admissions for hallucinogens show an increasing number reporting PCP as the primary drug of abuse. Of New York City AIDS cases involving adults (28,205 cases), 10,635 or 38 percent involve heterosexual intravenous drug users and 1,094 or 4 percent involve homosexual or bisexual intravenous drug users. The development of a Social Dysfunction Scale to assess drug abuse is discussed. 6 tables