Management, evaluation, and control of the aged heart require knowledge of the changes in regulation and control of the normal old heart. This study investigates, in man, the effect of age on the primary mechanism of cardiac control exerted by the sympathetic nervous system, and measures the response of hearts studied across a spectrum of ages (18-88) both at rest and after induced work loads using noninvasive measures of heart size and performance provided by echocardiography. BIBLIOGRAPHIC REFERENCE: Gerstenblith, G., Frederiksen, J., Yin, F.C.P., Lakatta, E.G. and Weisfeldt, M.L.: Echocardiographic assessment of a normal aging population. Circulation 56: 273-278, 1977.