Herman Goldstein's POP concept calls upon police to address a wide range of problems that threaten the safety and security of communities, including, but not limited to what is commonly viewed as serious crime. POP involves police in analyzing underlying conditions and features of community problems, followed by the development of strategies for responding to these problems through actions that focus on crime prevention as well as crime-solving. The first formal experimentation with the POP concept occurred in Madison, WI, in 1981 when Goldstein and his associates worked with the Madison Police Department to explore the community's response to drinking drivers and repeat sex offenders. In 1994, the U.S. Justice Department's Office of Community Oriented Policing Services (COPS Office) began to link funding for new police officers to the broad concept of community policing, which included POP as a key component. In many cases, however, the linkage of POP with community policing has blurred the distinction between the two concepts. This monograph discusses how POP is related to other movements in police reform and crime prevention, such as community policing, team policing, crime prevention through environmental design, situational crime prevention, and crime analysis and Compstat. This is followed by the identification and discussion of major challenges to the advancement of POP. These include setting an agenda for progress in POP; training in POP; and defining roles for the community, other government agencies, other government leaders, and prosecutors in the police agency's execution of POP. 200 references and appended analysis of the best submissions for the Herman Goldstein award for excellence in POP, 1993-99, a partial list of problem-focused literature, and a summary of interviews with selected POP practitioners and researchers