To determine the effects of aging and concentric hypertrophy on the reserve of the left ventricle < FA. 36 patients with hypertension (HT), 22 with hypertrophic cardiomyopathy (HCM) and 25 age-matched normal subjects (N) were studied by isoproterenol (ISP) infusion echocardiography. The end-diastolic I V relative wall thickness (RWT), fractional shortening (FS.), peak mitral How velocity during the rapid filling phase (R) and amai systole (A), and the A/R ratio were measured. At rest, the RWT and \ R were larger in groups H I and HCM than in group N. There were no signituant differences in age, heart rate (IIR). and FS among the groups. The A/R of all groups showed a good positive correlation with increasing age. The A/R of the HT group was also positively correlated with RWT. During ISP infusion, the HR, R, A, A/R and FS increased in all groups. The changes in R and FS were smaller in groups IIT and HCM than in group N. The change in HR in groups N and IIT, and the change in FS in all groups during ISP infusion were all inversely correlated with increasing age. The change in FS during ISP infusion was inversely correlated with RWT in the IIT group, but not in HCM. Thus, it was suggested that the impairment of LV reserve in patients with HCM is not only caused by concentric hy pertrophy and the aging process, hut also by other myocardial factors. © 1990, The Japanese Circulation Society. All rights reserved.