Impressive evidence supports the value of clinical preventive medicine, defined as the maintenance and promotion of health and the reduction of risk factors that result in injury and disease. Primary prevention activities deter the occurrence of a disease or adverse event, e.g., smoking cessation. Secondary prevention (screening) is early detection of a disease or condition in an asymptomatic stage so treatment delays or blocks occurrence of symptoms, e.g., mammographic detection of breast cancer. Tertiary prevention attempts to not allow adverse consequences of existing clinical disease, e.g., cardiac rehabilitation to prevent the recurrence of a myocardial infarction. Preventive services have decreased morbidity and mortality from both acute and chronic conditions. However, these services are underutilized for numerous reasons. Barriers to their use include physician, patient, and health system factors. The traditional disease/treatment model should be modified to incorporate more preventive services. The subsequent 2 parts of this review will discuss suggestions for integrating primary preventive services and screening into primary care practice.