The evaluation shows that BTC reduced arrests of probationers and parolees with substance-use problems. In BTC areas that administered more drug tests per person under supervision, probationers and parolees with drug abuse histories had a significantly lower likelihood of and significantly fewer actual arrests for any offense and for drug offenses. In BTC areas that administered more sanctions (immediate penalties for infraction of drug-use requirements) per person under supervision, probationers and parolees with drug problems had a slightly, but significantly lower likelihood of arrest and significantly fewer actual arrests for drug offenses. The evaluation concludes that BTC is an effective strategy for reducing drug arrests among probationers and parolees with drug-abuse problems. BTC strategies included frequent drug testing and the use of immediate sanctions for violation of conditions regarding drug use, so as to encourage abstinence and treatment participation. In support of the BTC initiative, the Maryland Legislature provided special funding to six of Maryland's largest counties and Baltimore City. Most of the funds were used for additional drug testing. The evaluation was based on a quasi-experimental comparison of probationers and parolees in BTC and non-BTC counties in the State. The comparisons focused on the differences in arrests between probationers and parolees in BTC and non-BTC counties. The analysis used statistical techniques developed and widely used by educational researchers to assess the impact of classroom innovations delivered in schools that vary widely in size, location, student-teacher ratio, etc., and to students who vary in intelligence, age, and prior preparation. 5 figures, 16 tables, and 14 references