Efficacy and acceptability of rilmenidine in populations with high cardiovascular risk has been established in short- or mid-term studies (1.5-6 months) enrolling relatively small numbers of patients. The present open study was undertaken to compare, on a larger scale, the efficacy and acceptability of a 12-month rilmenidine treatment in high-risk outpatients versus the results obtained in the general population and to check for unexpected adverse events. A total of 2,635 hypertensive patients (supine diastolic blood pressure [SDBP] > 90 mm Hg) were enrolled, including a high-risk population with 1,591 patients aged > 60 (60.3%), 1,007 patients with dyslipidemia (38.2%), 393 with diabetes (14.9%), 328 with chronic renal failure (12.4%), 301 with angina pectoris (11.4%), and 84 with chronic heart failure (3.2%). All patients were treated by rilmenidine 1 mg/day during the first 6 weeks; then (at 1.5 months), if SDBP was > 90 mm Hg, dosage of rilmenidine was 1 mg twice daily during the following 6 weeks. From month 3 to month 12, any other antihypertensive drugs could be added if SDBP remained > 90 mm Hg. In comparison with the general population, the percentage of high-risk patients whose monotherapy normalized blood pressure (SDBP < or = 90 mm Hg) was slightly lower at month 1.5 (58-66%, according to the risk group, vs 68% in the general population) and month 3 (73-82% vs 85%). At month 12, all treatments taken as a whole (monotherapy and combination therapy) led to the normalization of blood pressure in 94% of patients in the general population and in populations at risk.(ABSTRACT TRUNCATED AT 250 WORDS)