Data for the analysis were obtained from the York, P., Bureau of Police Incident Reports for September through December 1976. The Bureau received 8,788 calls for service during that period; however, the 1,284 cases analyzed in the study represented only the serious calls or crimes that warranted a detailed report and investigation. Bivariate relationships of clearance rate to crime, suspect, and operational variables were examined. Findings indicate that the presence of a witness and suspect description are the most critical variables affecting police apprehension. While the actual presence of a witness to a crime is not under the control of the police, the police can develop techniques that maximize their finding and eliciting the cooperation of witnesses. When there is no witness, the technical and investigative skills of the police are shown to be the primary determinants of apprehension productivity. Police management must recognize, however, that citizen cooperation has the highest priority in increasing apprehension productivity. An alternative to prevailing investigatory patterns that might enhance the citizen's coproduction role is the assignment of investigatory responsibility for major incidents to the officer responding to the call. Rather then merely completing a report, the officer on the scene would obtain witnesses and witness information, do followup investigations, and receive formal recognition for fulfilling these important responsibilities. Seventeen references are provided, along with tabular data.