Objectives First, to evaluate the prevalence of left ventricular (LV) hypertrophy, LV concentric remodelling and microalbuminuria in a selected sample of treated hypertensive patients with effective and prolonged clinic blood pressure (BP) control (BP < 140/90 mmHg). Second, to compare the prevalence of these markers of organ damage in patients with and without ambulatory BP (ABP) control, defined as average daytime BP < 132/ 85 mmHg). Design and methods Fifty-eight consecutive hypertensive patients who attended our hypertension outpatient clinic over a period of 3 months and were regularly followed up by the same medical team were included in the study. Obesity, diabetes mellitus, history or signs of cardiovascular or renal complications and major noncardiovascular diseases were the exclusion criteria from the study. Each patient underwent 24 h ABP monitoring, echocardiography and 24 h urine collection for albumin measurement. Results The prevalence of LV hypertrophy (LV mass index > 125 g/m(2) in both sexes), LV concentric remodelling (relative wall thickness > 0.45) and microalbuminuria (urinary albumin excretion < 300 mg/ 24 h) in this selected group of patients (32 men, 26 women; mean age 53 +/- 9 years; mean clinic BP 122 +/- 9/ 78 +/- 6 mmHg) was markedly low (6.9, 8.6 and 5.1%, respectively). The 26 patients with effective ABP control (group I) were similar to the 32 patients without effective ABP control (group It) in age, gender, body surface area, clinic BP, smoking habit, glucose, cholesterol and creatinine plasma levels. Prevalence of LV hypertrophy, LV concentric remodelling and microalbuminuria was lower in group I than in group II (0 versus 12.9% P < 0.01, 7.7 versus 9.4% NS, 3.8 versus 6.2% NS, respectively). Conclusions This study demonstrates that nonobese, nondiabetic hypertensive patients with an effective clinic BP control have a very low prevalence of target organ damage and that LVH is present only in individuals with insufficient ABP control. J Hypertens 2000, 18:803-809 (C) Lippincott Williams & Wilkins.