Metaanalyses have indicated that ACE inhibitors are more effective than other first-line therapies in reducing left ventricular hypertrophy (LVH). The average treatment period, however, was only approximately 6 months. The aim of the present study, therefore, was to clarify the time course and degree of reversal, and primarily to find out in how many patients a complete normalization of LVH can be achieved. Secondly, we sought to determine whether atrial enlargement can be reduced. Previously untreated hypertensive patients (mean age 46.3 +/- 9 years, eight women, 15 men) with echocardiographically confirmed LVH (left ventricular mass index ([LVMI] > 125 g/m2 for men; > 110 g/m2 for women) were prospectively treated over a 3-year treatment period with quinapril. Nine patients received 10 mg quinapril, 12 received 20 mg of quinapril daily, and five patients additionally received 25 mg hydrochlorothiazide. The time course of changes in LVMI, relative wall thickness, left atrial size, fractional shortening, and diastolic function was evaluated and ambulatory blood pressure monitoring (ABPM) and an exercise test were performed every 6 months. After a mean treatment period of only 7.5 months, there was a significant (P < .001), 17.5% decrease in LVMI with a further continuous and significant (P < .001) decrease of 38.6% after 38.3 +/- 3 months of therapy. In 90.5% of the patients a complete reversal of LVH was achieved. Fractional shortening increased significantly, the maximum being 14.6% after 38.3 +/- 3 months. The peak early/atrial velocity (E/A) ratio increased significantly (P < .01) after just 7.5 +/- 3.1 months with no further changes during follow-up. There seemed to be a parallel change with the decrease in left atrial dimension, where the most important decrease occurred after only 7.5 +/- 3.1 months (P < .01), with a further continuous reduction. Our study clearly shows that maximum reversal of LVH is a time-consuming process and that an essential goal of antihypertensive therapy should be not only a reduction in LVH but also a normalization in LV mass, left atrial size, and in diastolic dysfunction.