Four years of activity in the one-day hospital (ODH) and the several-day hospital care (SHC) of the Hypertension Clinic at the Hôpital Saint-Joseph, Paris, were evaluated and compared. All data were recorded using the computerized Artemis system. Evaluation was performed by means of two prospective studies: a controlled trial of 121 patients randomized to either ODH or SHC, and a prospective follow-up study of 633 patients. Criteria for admission to the controlled study were: diastolic BP between 95 and 120 mmHg, age between 30 and 65 years, no anti-hypertensive treatment at first visit, no major cardiovascular or renal complication and no suspicion of secondary hypertension. Similar criteria applied to the uncontrolled study. The results, assessed after 2 years, were the same in both studies, with a drop-out rate of about 15%, a mean diastolic BP lower than 95 mmHg in 80% of the patients and a bodyweight reduction of about 1 kg in obese patients. The percentage of smokers who stopped cigarette smoking was higher in the SHC groups than in the ODH groups. It is concluded that the ODH system is effective in the initial management of hypertensive patients but that greater educational efforts are needed to effectively reduce cigarette smoking in OHD patients and bodyweight excess in both OHD and SHC patients.