The study identified as many variables as can be justified theoretically for use as controls to isolate the independent effects of unionization on police compensation. Labor supply variables were opportunity wage, measured as the average earnings of service employees within the county for 1975; nature of the labor force, measured as percentage nonwhite; and quality of the labor force, measured as median years education, 1970. Labor demand variables were population size in thousands for 1973; per-capita personal income estimated for municipalities for 1972; and crime rate, measured as the number of index offenses per 100,000 population, 1975. Police unionization was measured as the percentage of police officers belonging to employee organizations that bargain over compensation either formally or informally (1977). Labor demand pressures, particulary per-capita income and community size, were found to be the most important influences on compensation levels. The unionization measure reached statistical significance for two of five equations, but for overall compensation, fully unionized departments received only about a 1 percent financial advantage. Subsequent analysis also revealed that unionized departments operating under a formal contract are recipients of a compensation differential, but that departments affiliated with national employee organizations do less well financially than strictly local organizations. Tabular data, footnotes and 26 references are provided.