The study found that drug use and related problem behaviors were not significantly different for boys and girls. Boys and girls did not differ in their use of cigarettes, alcohol, cannabis, ecstasy, inhalants, and amphetamine; however, boys were more likely to report hashish use, and girls were more likely to report the use of prescription drugs, cocaine, and heroin. No gender differences were found for binge drinking, driving a car after drinking or being a passenger in a car after the driver had been drinking, selling drugs, deterioration of relationships with friends and family, gambling, taking loans, or using personal money to buy drugs. Further research, such as surveillance monitoring, is needed in order to understand which drugs are being used and how (e.g., injection drug use) among male and female adolescents across locations, programs, and over time. Such research is important for matching clients to treatment services, as well as for controlling the spread of infectious disease. Data were collected during a 15-month period in 2005 and 2006 and involved girls and boys between the ages of 13 and 18. Data were obtained from a self-report questionnaire completed during their intake interview upon entering drug treatment. 2 tables and 17 references