Data were collected primarily through interviews with 205 officers and 85 prosecutors in 16 jurisdictions. The study concluded that police often do not supply prosecutors with the amount and kind of information needed; that the relationship creates intense interpersonal animosity, interorganizational conflict, and noncooperation; and that much of the conflict results from mutual doubt and suspicion about the competence, motives, and dedication of personnel in the other agency. However, eliminating inconsistencies between police and prosecutors may not be feasible or desirable where controversial laws are involved. Police and prosecutors must attempt to select weak and low-priority cases out of the prosecution process at the earliest point, while communicating on serious (mutually agreed-upon) cases. Police training programs should afford police opportunities to learn directly from local prosecutors, while prosecutors and police should communicate to each other their special knowledge of each case and its disposition. The police role in a case should be redefined as ending with conviction rather than arrest. A bibliography is supplied. (Author abstract modified)