The first paper uses existent secondary sources to critically examine what is known and not known about the early history of detectives. Present-day detectives are traced from the introduction of the constable following the Norman Conquest in 1066 to the formation of detective units in England and the United States in the mid-1800's. The literature review notes that arguments put forth in both countries to justify public, centralized, preventive policing centered on efficiency, effectiveness, and equity. A second literature review -- on the current nature of detective operations -- examines the methods repertoire from which all detectives choose, including forensic aids, technical information systems, informants, interviews interrogations, instigation, and surveillance. It shows that detectives are poorly trained and managed, and considers the potential impact of detectives if these problems could be remedied. One paper looks at detectives' success in solving crimes, concluding that standard investigative techniques such as interviewing witnesses and informants, discussing cases with department members, and checking files are strongly related to arrests. The organization of the investigative function in larger U.S. police agencies (patrol division handling preliminary investigation and detective division the followup) and the triage hypothesis (which differentiates types of cases) are also discussed. A paper examining criminal investigation research in England and Wales looks at research which analyzes how investigations are pursued, how investigators spend their time, and how crimes are cleared up; it also summarizes research that has tried to establish what factors affect performance. A final paper on developments in crime and criminal investigation in The Netherlands presents background material on the rising crime rate and discusses the role of criminal investigation in solving crimes; it considers the question of whether customary assumptions about the relationship between detection and crime control are correct. The bibliography focuses on public and private detectives, detective units and agencies, detective fiction, and criminologist. Numerous references and tables.