The objective of the study was to assess the influence of left ventricular (LV) hypertrophy regression on exercise capacity in hypertensive patients. Doppler echocardiography was performed at rest and during exercise in 51 patients with electrocardiographic LV hypertrophy before and after 1 year of randomized blinded losartan- or atenolol-based antihypertensive treatment. After 1 year, blood pressure was comparably reduced by 32/14 and 27/13 mmHg, respectively, in the losartan and atenolol groups, but the atenolol group had higher mean LV mass index (118 vs 103 g/m2) and lower LV ejection fraction (61% vs 67%) and midwall shortening (15.8% vs 16.8%) (all p<0.05). Resting diastolic Doppler indices remained unchanged and did not differ between the groups. Peak oxygen uptake during exercise was virtually unchanged after 1 year and did not differ between the groups in spite of a lower peak exercise heart rate in atenolol-treated patients. In multivariate analysis, higher peak oxygen uptake at 1 year was associated with lower body mass index, and higher systolic blood pressure and shorter isovolumic relaxation time at peak exercise (multiple R2 = 0.51, p<0.01), while age, gender, heart rate increase during exercise, reduction in LV mass and study treatment did not enter. In conclusion, reduction in blood pressure and LV mass induced by losartan or atenolol treatment was not accompanied by improved exercise capacity after 1 year. The results may be explained by persistent impairment of myocardial relaxation influencing exercise capacity.