One hundred and seventy-four patients who were receiving drug therapy for hypertension were asked to restrict their sodium intake for three months. At the end of that time their drug therapy was replaced with enalapril and the dose of the drug "titrated" to obtain a diastolic blood pressure of less than 90 mmHg. Sodium restriction caused a small fall in blood pressure and could be used as sole therapy in only 6% of patients. Enalapril therapy was instituted without problems and control of blood pressure below 90 mmHg was achieved in 62% of persons with monotherapy. The number of tablets of enalapril that were taken was reduced from 5.9 to 2.7; in most patients these were taken once a day. There were few side-effects and no depression of white cell count, no proteinuria and no deterioration of renal function. Seventy-six per cent of patients preferred the new regimen either because they felt better than with their previous therapy (52%) or because of the more simple regimen (24%). Enalapril was an effective, well tolerated antihypertensive agent and potentially has a major role to play in the management of patients with high blood pressure.