THE VARIATION AMONG CONTEMPORARY POLICING SYSTEMS IS DESCRIBED, AND THEORIES DEVELOPED TO EXPLAIN THESE VARIATIONS ARE REVIEWED. STUDY OF THE NATURE OF POLICE WORK HAS EMPLOYED THREE DIFFERENT MEASURES OF FUNCTION--THE NUMBER OF PERSONNEL ASSIGNED TO DIFFERENT SPECIALIZED UNITS, THE KIND OF OCCASIONS THAT TRIGGER POLICE MOBILIZATIONS, AND THE NATURE OF OUTCOMES FROM MOBILIZATIONS. THE RESEARCH HAS ALSO SHOWN THAT THE BULK OF POLICE PERSONNEL ARE ASSIGNED TO PATROL, AND STATE IMPOSITION OF TASKS ON THE POLICE HAS DECLINED IN ALL COUNTRIES DURING THE PAST CENTURY. THE UNITED STATES IS THE ONLY COUNTRY THAT HAS FAILED TO ESTABLISH A NATIONAL SYSTEM OF POLICING. CENTRALIZATION DOES NOT APPEAR TO BE THE WAVE OF THE FUTURE IN THE NATIONAL SYSTEMS OF WESTERN EUROPE AND NORTH AMERICA, NOR DOES IT APPEAR TO BE RELATED TO THE CHARACTER OF GOVERNMENT OR PERFORMANCE OF THE POLICE. POLICE CONTROL MECHANISMS ALSO VARY CONSIDERABLY IN TERMS OF CENTRALIZATION AND TYPE OF PERSONNEL INVOLVED. THE ESSAY CONCLUDES BY ASSESSING THE CONTRIBUTION MADE BY COMPARATIVE AND HISTORICAL STUDIES TO WHAT IS KNOWN ABOUT POLICE FUNCTION, ORGANIZATION AND CONTROL AND SUGGESTS AN AGENDA FOR NEEDED FUTURE RESEARCH ON THE SUBJECT. REFERENCES AND A SELECTED BIBLIOGRAPHY ARE APPENDED. (AUTHOR ABSTRACT MODIFIED - MJW)