The basic data set includes 19 items that cover demographic information; primary, secondary, and tertiary drugs and their route of administration, frequency of use, and age at first use; the source of referral to treatment; the number of prior treatment episodes; and the service type, including the planned use of methadone. The supplemental data set consists of 15 items that include psychiatric, social, and economic measures. Four substances accounted for more than 90 percent of the admissions in 1997. These included alcohol (48 percent); opiates, primarily heroin (16 percent); cocaine (15 percent); and marijuana/hashish (13 percent). Forty-four percent of the alcohol admissions reported secondary drug abuse as well. The proportion of admissions for alcohol alone declined from 37 percent in 1992 to 27 percent in 1997. Alcohol admission rates were generally highest in the west, midwest, and northeast. However, a number of States have experienced substantial declines in admission rates for primary alcohol use. The proportion of opiate admissions surpassed that for cocaine admissions in 1997 for the first time since data collection for the Treatment Episode Data Set began in 1992. The proportion of admissions for primary marijuana use more than doubled between 1992 and 1997, form 6 percent to 13 percent. Finally, 32 percent of inhalant admissions had used inhalants by the age of 12; another 30 percent had used inhalants by age 14. Figures, tables, and appended methodological information