Minoxidil was used in 25 patients with severe hypertension whose blood pressure (BP) could not be controlled with conventional treatment or who suffered from intolerable side effects during treatment with other drugs. In 6 patients minoxidil was withdrawn after a short time owing to side effects or because hypertension could be controlled by regular dialysis treatment. The remaining 19 patients were treated with minoxidil for 0.5-4.5 years. The hypotensive effect of minoxidil in combination with beta-blockers and diuretics was good or acceptable in all patients. Neither orthostatic hypotension nor development of resistance was observed. Minoxidil was well tolerated in one patient with porphyria and in two patients who have had the hydralazine syndrome. Eighteen patients had kidney failure with elevated serum creatinine. With one exception the uraemia progressed if the serum creatinine level was above 300 mumol/litre at the start of the treatment. All patients tended to develop oedema, but this was controlled by concomitant diuretic therapy. Eighteen patients developed hypertrichosis. No other significant side effects were observed. One patient died and two patients developed pericarditis in the highly uraemic phase in connection with the start of dialysis. Neither the death nor the cases of pericarditis can be attributed to minoxidil. Minoxidil was found to be effective in severe hypertension in connection with advanced renal disease and can be considered as a valuable addition to the established therapeutic arsenal for treatment of severe hypertension.