I first took up walking as a means of escape. After a busy morning in my office, I found it refreshing to take a stroll at lunchtime, to breathe the fresh air and feel the sun. Another walk in the cold night air was, I discovered, an exhilarating way to unwind. I'll never forget the feeling I got one winter night as I walked the deserted streets after many grueling hours at the hospital. I suddenly realized that I no longer felt tense or tired. All the worries about my patients' illnesses, as well as my own personal cares, seemed to evaporate as quickly as the smoky vapor of my breath in the frosty night. As I incorporated walking into my schedule, not only were my spirits lifted, but my weight and blood pressure were gradually reduced. I began reviewing the medical literature on walking. From this research, and my clinical observations as a family physician, I found that it is possible to walk your way to better health, a trimmer body and a longer life -- no matter what your age. Walking -- like swimming, bicycling and running -- is an aerobic exercise which builds the capacity for energy output and physical endurance by increasing the supply of oxygen to skin and muscles. Such exercise may be a primary factor in the prevention of heart and circulatory disease. As probably the least strenuous, safest aerobic activity, walking is the most acceptable exercise for the greatest number of people. Walking at comfortable speed improves the efficiency of the cardio-respiratory system by stimulating the lungs and heart, but at a more gradual rate than most other forms of exercise.