Once-daily minoxidil administration was added to the treatment regimen of 11 patients with hypertension that was inadequately controlled by nadolol 160 mg and chlorthalidone 50 mg given once daily. Additional diuretic therapy was needed by five patients. During treatment without minoxidil and at three and six months of maintenance minoxidil therapy, respectively, 24-hour postdose supine blood pressure fell significantly (P less than .01) from 142 +/- 19/96 +/- 6 mm Hg to 132 +/- 16/87 +/- 4 and 131 +/- 12/87 +/- 4 mm Hg, and home recordings showed that minoxidil induced a mean increase of about 5 beats/min in heart rate. Resting plasma renin activity was not significantly altered. High-density lipoprotein (HDL) cholesterol increased from 31.6 +/- 9.9 to 35.2 +/- 10.9 mg/dL (P less than .05) and to 34.4 +/- 11.3 mg/dL (NS), and low-density lipoprotein (LDL) cholesterol decreased from 146 +/- 36 to 136 +/- 32 mg/dL (P less than .05) and to 126 +/- 35 mg/dL (P less than .01) over the same periods. At six months, approximately 20% changes in ratios of HDL cholesterol to either LDL or total cholesterol were seen. These changes occurred despite a three-pound mean increase in body weight (P less than .05); these alterations are potentially beneficial in terms of reducing the estimated risk of coronary artery disease.