In a multicentre open trial involving 229 investigators, cicletanine, a new antihypertensive agent, was administered orally in doses of 50 to 100 mg/day either alone (1,238 patients) or combined with another drug (430 patients). In this second group of patients with essential hypertension whose BP had not been normalized by a beta-blocker (n = 157), a calcium inhibitor (n = 67), an angiotensin-converting enzyme inhibitor (n = 134) or an alpha-blocker (n = 7), cicletanine normalized BP (less than 160/95 mmHg) in 48.8% of the patients and significantly lowered BP values which fell from 177.7 +/- 15.9/103.3 +/- 6.3 mmHg to 157.2 +/- 17.6/88.8 +/- 8.7 mmHg. The addition of cicletanine to treatments with beta-blockers, calcium inhibitors and angiotensin-converting enzyme inhibitors normalized BP in 48%, 52% and 47% of patients respectively. A significant reduction of symptoms was noted, notably as regards headache, dizziness, palpitations, lower limb oedema, asthenia, auditory disorders and dyspnoea. The side-effects reported (headache, dizziness, gastralgia, nausea, pruritus) were minor and non-specific; they accounted for the withdrawal of only 8 patients. The only significant, though moderate, biochemical variations observed were decreases in natremia and cholesterolaemia unconfirmed by qualitative analysis. Altogether, cicletanine proved to be effective and well tolerated when administered in combination with other antihypertensive drugs belonging to three main therapeutic classes.