Treatment of severe hypertension is beneficial, but reversibility of target-organ damage has not been characterized. Serial studies were performed in 15 patients with severe essential hypertension (age of 56 +/- 3 years, mean +/- SEM) treated for 1 year with 60 to 150 mg/day of continuous-release nifedipine; 3 patients required 50 mg of chlorthalidone/day to lower diastolic blood pressure (BP) to less than 95 mm Hg. Left ventricular (LV) structure and function was evaluated with two-dimensional-directed M-mode echocardiography, digitized from videotape and analyzed blindly. BP was markedly reduced from 194 +/- 8/115 +/- 4 to 146 +/- 4/88 +/- 14 mm Hg (p less than 0.0001) and maintained at this level for 1 year. Posterior wall and septal LV thickness, elevated at entry (12.9 +/- 0.1 and 13.4 +/- 0.1 mm), dropped steadily over 1 year into the normal range (10.0 +/- 0.03 and 11.2 +/- 0.1 mm, p less than 0.001). LV mass index, above 95% for normals at entry, decreased by 19% at 6 months (129 +/- 10 to 104 +/- 7 g/m2, p less than 0.01), and remained at this level at 1 year. LV fractional shortening rose steadily over 1 year from 34 to 42% (p less than 0.02). Atrial natriuretic peptide, which reflects LV filling pressures, was markedly elevated at entry, but was significantly reduced by 6 months (76 +/- 22 vs. 45 +/- 14 pg/ml, p less than 0.05). Sustained reduction of arterial BP with continuous-release nifedipine for 1 year normalizes LV mass, improves LV systolic function, and reduces circulating levels of atrial natriuretic peptide.