The antihypertensive efficacy, lipid effects, and safety of doxazosin, a selective alpha 1-inhibitor for the reduction of coronary heart disease (CHD) risk in hypertensive patients, was assessed in a general medical practice setting. Seven hundred seventy-one patients were entered into the study, which involved three phases: (1) a 2-week baseline period, (2) an 8-week period in which patients received doxazosin, 1 to 8 mg once daily, and (3) a 4-week maintenance period. From baseline to final visit there was a highly significant 27% reduction (p less than 0.001) in calculated CHD risk based on the Framingham equation as a consequence of doxazosin's favorable effects on both blood pressure and serum lipid levels. Efficacy and toleration of doxazosin therapy were good to excellent in most patients. The investigators' global assessment of efficacy of once-daily doxazosin therapy was excellent or good for 82% of patients and fair or poor for only 18% of patients. After 12 weeks, 83% of the patients were considered therapy successes (sitting diastolic blood pressure either less than or equal to 90 mm Hg or greater than or equal to 10 mm Hg reduction not reaching less than or equal to 90 mm Hg) at a mean daily dose of 3.5 mg. Seventy-one percent achieved "normalized" blood pressure control (sitting diastolic less than or equal to 90 mm Hg with a decrease of greater than or equal to 5 mm Hg) at a mean dose of 3.1 mg once daily. By the final treatment visit, systolic/diastolic blood pressures of efficacy evaluable patients were reduced by 20.6/15.3 and 21.0/15.4 mm Hg from a mean baseline of 166/104 and 165/104 mm Hg in the sitting and standing positions, respectively (p less than 0.05). Total cholesterol was significantly decreased (p less than 0.01). Most side effects were mild or moderate and disappeared with or were tolerated on continued therapy. The investigators' global assessment of patient toleration of doxazosin treatment was excellent or good for 89% of the 763 patients evaluated and fair or poor for only 11% of patients. The most commonly reported side effects were headache (8%) and dizziness (7%). No clinically significant laboratory changes were apparent, and no trends were observed with regard to organ systems or correlations with dose or duration of treatment.