Following a review of the published literature on substance use by young people under the care of social service agencies, preliminary findings from an evaluation of a drug prevention intervention among people living in a residential care establishment in Great Britain are presented. This evaluation involved the completion of questionnaires by males and females between 14 and 19 years of age. Of the 15 young people, 13 (86 percent) had used illegal drugs; 10 (67 percent) had used an illegal drug in the past month, and 6 (39 percent) had used an illegal drug in the past week. Nearly half began using drugs at the age of 12 years or younger. Most used a range of different drugs, including cannabis, speed, ecstasy, LSD, cocaine, magic mushrooms, and poppers. The drug intervention, designed to change drug-using behaviors and opinions about drug use, was successful. A comparison of the evaluation findings with other research data suggests substance abuse by young people under the care of social service agencies is higher than that of the general youth population. Although substance abuse by these young people is generally recreational and not considered by the young people themselves to be problematic, the level of use may place them at increased risk of movement into more problematic drug use in the future. The feasibility and implications of implementing drug interventions with young people looked after by social services are discussed. 23 references and 2 notes