The officers were between 21 and 52 years of age and were free from known cardiovascular or other serious diseases or disabilities. They agreed to be evaluated initially and again after 20 weeks of physical training. Testing sessions, which were conducted at the Institute for Aerobic Reseach, Dallas, Tex., included the following test battery: cardiovascular-respiratory, pulmonary function (spirometry), body composition, blood (serum), and motor ability. The officers also completed medical forms which gave information about their family histories of heart disease and smoking habits. To determine coronary risk, the data were compared to standards recommended by the American Heart Association and the Cooper Clinic. To compare police officers' fitness levels, the data for the general population, Los Angeles County Sheriff's Department personnel and highway patrolmen, and prison inmates were plotted on the norm scales developed for police officers. Younger police offices tended to be of average risk for coronary heart disease and were average in physical fitness compared with the general population. Middle-aged police officers were shown to be at higher risk and were lower in physical fitness than the general population. The results from this investigation support the need for physical fitness and preventive medicine programs for police officers. Five tables and 26 references are appended. (Author abstract modified)