Four substances accounted for 91 percent of all TEDS admissions in 1999: alcohol (47 percent), opiates (16 percent, primarily heroin), cocaine (14 percent), and marijuana/hashish (14 percent). Polydrug use was reported by 54 percent of all TEDS admissions in 1999, with alcohol, marijuana/hashish, and cocaine being the most common secondary substances reported. Adolescent admissions for substance abuse increased between 1994 and 1999, which was attributable to both increased admissions that involved marijuana and increased referral to treatment through the criminal justice system. The rate for alcohol admissions declined by 19 percent between 1994 and 1999. Alcohol admission rates were generally highest in the Pacific Northwest, North Central, and Northeast. The proportion of TEDS admissions for primary opiate abuse increased from 14 percent in 1994 to 16 percent in 1999, slightly exceeding the proportion of admissions for primary cocaine abuse. Heroin admission rates were highest in the Pacific and Middle Atlantic States. The proportion of admissions for primary cocaine abuse declined from 18 percent in 1994 to 14 percent in 1999, with cocaine admission rates being generally highest in the Middle Atlantic and some Southern States. The proportion of admissions for primary marijuana abuse increased from 9 percent in 1994 to 14 percent in 1999. The proportion of admissions for abuse of methamphetamine/amphetamine admission rates increased slightly from 3 percent to 5 percent between 1994 and 1999. 36 tables, 36 figures, and appended TEDS data elements