The lack of exercise by most Americans is a major contributing factor to many chronic diseases. Physicians are now prescribing exercise for patients just as they would drugs. Compliance with any exercise program depends on realizing the needs and goals of the individual. The fundamental principles of an exercise prescription apply to all persons regardless of age, sex, or level of fitness. A systematic manipulation of the components of frequency, duration, intensity, and progression with periodic reevaluation allows the program to be individualized. The guidelines for the program should include all of the components of health-related physical fitness. These include cardiorespiratory endurance, body composition, muscular strength and endurance, and flexibility. A program for exercise should fit the lifestyle of the patient and be a life-long prescription.