The economic impact of TAP was studied by examining costs and benefits of diverting offenders from the criminal justice system into drug abuse treatment. All treatment programs were required to submit client monitoring data for clients screened between June 1990 and May 1991; during this 1-year period, 259 offenders were admitted to TAP. Programs provided monitoring data on clients at screening, 3 months into the program, and at program discharge. A client outcome study was also conducted that involved 112 of the 259 offenders. TAP costs included direct expenditures for treatment, drug testing, program overhead, case management services, medical expenses, and screening and assessment. TAP benefits affected not only clients in treatment but also family members, friends, and society. These benefits included lower criminal justice costs, increased productivity, improved health status, increased behavioral functioning, and reduced fear of crime. TAP also minimized the number of jail days served, the number of arrests, crime victim costs, and the number of lawyer visits. Estimated benefits of TAP outweighed costs in the short term. Depending on the assumptions made, the cost-benefit ratio for TAP ranged from 1.4 to 3.3. Cost-effectiveness data per jail day saved are provided. 34 references and 8 tables