Data were collected from site visits, official records, and formal and informal interviews. Of the 16 original programs, 6 were chosen for intensive review. These were in Detroit, Fort Worth, Tex.; Jacksonville, Fla.; Kansas City, Mo.; Overland Park, Kans.; and Los Angeles. The number of suspects encountered ranged from 96 to 554; the number involved in transactions ranged from 84 to 284. Fort Worth arrested 91 percent of those encountered; the other sites arrested about 50 percent. In all but one site, suspects were active criminals with two or more prior felony arrests. Automobiles and portable and frequently stolen items were the most common types of property purchased. Property transactions ranged from 126 to 806; the median price paid per transaction ranged from $100 to $400. The median value of recovered property ranged from $450 to $7,000. The projects successfully arrested and convicted a fairly large number of criminals. Overall, findings indicate that such proactive undercover operations can be and have been effective in arresting certain types of criminals, particularly career thieves engaged primarily in burglary, larceny, and/or motor vehicle theft. The high dollar value of recovered property suggests that the approach is cost-effective and can result in a substantial return on law enforcement investment. Advantages and disadvantages of these programs are discussed. Tabular data and additional research materials and data are appended.