Objective The aim of the study was to evaluate the prevalence of left ventricular hypertrophy (LVH) in treated patients with good blood pressure (BP) control during multiple home BP (HBP) measurements and during 24-h ambulatory BP monitoring (ABPM), but with unsatisfactory BP control in the clinic. These patients were compared with treated hypertensives whose BID was well controlled under the three circumstances. Methods Seventy-two treated consecutive patients (group 1, age 56 +/- 10 years) with clinic BP values greater than or equal to 140/ 90 mmHg, and a difference between clinic and self-measured HBP > 10 mmHg for diastolic blood pressure (DBP) and/or > 20 mmHg for systolic blood pressure (SBP), underwent the following procedures: (1) clinic BP measurement; (2) routine diagnostic work-up; (3) HBP monitoring; (4) 24-h ABPM; (5) echocardiography. Thirty-five hypertensive patients with satisfactory BP control according to clinic (< 140/90 mmHg), HBP (less than or equal to 131 / 82 mmHg) and ABP criteria (less than or equal to 125/79 mmHg) were included as the control group (group 11, age 55 +/- 9 years). Results In group I, 33 subjects out of the 72 (46%) with clinic BP > 140/90 mmHg had BP values controlled outside the clinic (23 according to HBP criteria and 22 according to ABP criteria). The prevalence of LVH (LV mass index > 134 g/m(2) in men and > 110 g/m(2) in women) was significantly higher in these patients (115.1 versus 2.8%, P < 0.01) than in group II (BP also controlled in the clinic), despite the fact that HBP and ABP were reduced to similar levels in the two groups. Conclusions Our data provide evidence that treated hypertensive patients with good BP control at home or during ambulatory monitoring, but incomplete BP control in the clinic, have more pronounced cardiac alterations than patients with both clinic and out of the clinic BP control. This finding offers a new piece of information about the diagnostic value of BP measurement in the clinic to assess BP control during anti hypertensive treatment. (C) 2003 Lippincott Williams Wilkins.