Project objectives were to determine whether hidden cameras (1) increased robbery clearances, (2) increased convictions, (3) reduced the incidence of robbery in the treatment sites and in the city as a whole, (4) affected the potential risk of injury in a robbery situation, and (5) reduced the cost of processing and prosecuting robbery cases. The emphasis of this review is on the relationship between environmental factors and criminal behaviors. The project used an experimental design. A total of 150 businesses were identified as likely to be robbed. One-half were given hidden cameras while the other half were not treated. The experimental period was June 1976 to April 1977. About 3 months after camera installation, one-half of the cameras were moved randomly from their original sites to previously untreated (control) sites. Additionally, the study compared the level of commercial robberies in Seattle to the crime levels in other cities of 250,000 population or more. Findings showed that monthly robbery rates decreased 38 percent in the 11 months after installation compared to the 11 months preceding installation. Forty-eight percent of the offenders involved in robberies at hidden camera sites were convicted, compared to 19 percent of the offenders at the control sites. Fifty-five percent of robberies at the treatment sites were cleared by arrest, compared to only 25 percent in the control sites. The conclusions appear to be supported by the data; however, the study does not help in identifying potentially important intervening variables, such as police patrol and surveillance. Still, the effort has provided generalizable results and a replicable planning and implementation process. Tabular data and footnotes are not provided.