Inspection and maintenance (I/M) programs are intended to minimize motor vehicle emissions through the identification and repair of defective vehicles. Laboratory studies have indicated I/M has the potential to reduce hydrocarbon and carbon monoxide emissions by in excess of 25%; however, many of the I/M programs currently operating in the United States may be achieving only minimal emission reductions.In order for the “theoretical” benefits of I/M to be achieved, certain program design features and enforcement procedures are necessary. The important elements of an effective I/M program include stringent emission standards, effective inspection procedures, effective repair requirements, minimal use of waivers, an effective compliance mechanism, reasonable inspection fees, and data analysis and surveillance procedures that identify individuals who are improperly performing inspections and repairs. In addition, the agency responsible for the program must have the resources necessary to ensure that corrective action is taken when problems are identified.I/M programs recently implemented in the state of Alaska represent an attempt to maximize emission reductions in “decentralized” or “private garage” I/M programs. Preliminary results indicate that significant benefits are being achieved. Data analysis is also identifying those mechanics who are reporting invalid data, failing to repair an excessive number of vehicles, or reporting visual inspection failure rates that are much higher or much lower than the norm.