A police juvenile unit is any organizationally definable unit within a police department having primary responsibility for handling juveniles or juvenile cases. Study data were collected via a literature review, a national mail and telephone survey of police departments, field visits to police departments, and case studies of police departments across the country and case studies of selected departments. Departments without juvenile units were included to highlight questions and issues that might otherwise have gone unrecognized. The concept of a separate juvenile justice system dates from the beginning of the 20th century, and responses to the mail survey suggest that most city and county police departments serving populations of more than 100,000 currently operate juvenile units. The telephone interviews and field visits indicate that most units perform one or more of three functions (investigation, screening, and program operation) through which the units try to achieve several primary goals. However, the literature review reveals that little empirical data exist on the effectiveness of juvenile unit operations. Case studies, including statistical data, of the investigative functions, and the screening function, are reported. The study suggests the baseline data needed on juvenile units for future research and recommends a specific monitoring approach that should be established as a necessary step preceding any further evaluation. Additional areas are recommended as priorities for future research. Footnotes, tables, and 42 references are supplied.