A multicenter study of doxazosin in the treatment of essential hypertension in France. This study was designed to assess the efficacy and tolerance of doxazosin in patients with mild, moderate, or severe essential hypertension in a general practice setting. Ninety-six adults of a mean age of 55 1/2 years took part in the 14-week study, consisting of a placebo phase (2 weeks), a dose-adjustment phase with doxazosin (8 weeks), and a maintenance phase (4 weeks). Doxazosin, at a final mean daily dose of 3.4 mg, produced a significant (p less than 0.05) reduction in blood pressure at all points of measurement during the study. The mean change in sitting blood pressure at the end of treatment was -15.4/-15.8 mm Hg. Of the 85 patients who could be categorized as a success or failure, 78 (92%) were considered a therapeutic success; 78 (89%) of the 88 efficacy-evaluable patients demonstrated an improvement in the severity category of their hypertension. Treatment with doxazosin produced a reduction in serum cholesterol (-3.1%) and triglyceride (-3.8%) levels, although these changes did not attain statistical significance. The calculated probability of developing coronary heart disease in 10 years (according to the Framingham equation) was significantly (p less than 0.001) reduced by 22%, from 16.7 chances per 100 (baseline) to 14.3 chances per 100 (final visit). Twenty-six patients (27.1%) reported side effects that were possibly related to treatment, the most prevalent of which were vertigo (7.3%) and headache (6.3%). In four (4.2%) patients the dose of doxazosin was reduced and two (2.1%) were withdrawn prematurely. The investigator's assessments of tolerance was reduced and two (2.1%) were considered to be excellent or good in 85 (88%) patients. 