Studies have indicated that men in sedentary occupations are more liable to have coronary heart disease than those in occupations requiring moderate to heavy physical activity. To test this hypothesis a study was conducted of the death rates among clerks, switchmen, and section men employed in the railroad industry. MORRIS, et al.,1 demonstrated an association between the physical activity required by an occupation and the incidence of coronary heart disease over a period of two years among bus drivers and conductors employed by the London Transport Executive. Additional studies of postmen on the one hand, and telegraphers, telephonists, clerks, and supervisory personnel of the postal service on the other, also indicated a higher incidence of coronary heart disease among men in the more sedentary jobs than among men in the occupations requiring greater physical activity. In addition, it was found that men in sedentary occupations had less angina pectoris and a higher death rate during the first three months after an initial coronary attack than men in the more active occupations. Since that time, results of other studies in Great Britain2-5 and in the United States67 have supported the thesis proposed by Morris that men in physically active jobs have a lower incidence of coronary (ischemic)