A previous investigation of the French League against Hypertension has shown that only 27% of the hypertensives aged below 64 years and 19% of those aged above 64 years have their BP controlled under treatment (BP < 140/90 mmHg). The international, prospective, randomised HOT study aims at assessing the optimal diastolic BP (DBP) level during active antihypertensive treatment to reduce at the best the cardiovascular morbidity and mortality. The study is on-going, with a completion of inclusions. The BP measurements are performed by oscillometric method with the D2 international BP device, HESTIA. At enrollment, only 52% of the hypertensives were treated, their mean BP level being 161/99 mmHg +/- 18/9 mmHg (n = 10,005). On randomisation, two weeks after the treatment withdrawal, BP was 170/106 +/- 15/4 mmHg. Six months later, under treatment, BP was 150/84 +/- 10/7 mmHg with a mean decrease of 11/15 mmHg compared to values under previous treatment. Depending on the randomisation groups which are defined by different DBP objectives, 87.5 to 92.2% of the patients have a BP normalisation (DBP < or = 90 mmHg) after one year of treatment. Five explanations may be proposed for the better BP control observed in the study compared to the results at inclusion, reflecting the general practice: (1) the fact that the patient is free to participate and has been informed may have improved the compliance, (2) the patient's follow-up was reinforced during the first weeks, (3) the protocol is based on the treatment initiation by a dihydropyridine with a long duration of action: felodipine, (4) the BP objectives are rigorously defined by a DBP between 80 and 90 mmHg depending on the randomisation group whereas in general practice, the physician may have a smoother objective mainly aiming at improving tolerability, (5) the larger use of a bi-therapy. CONCLUSION. The more ambitious aims of BP control (DBP < or = 90, 85, 80 mmHg) in this study have induced a treatment intensification with a better BP control.