To date, more than 5000 patients have had experience with enalapril. Over 1000 subjects have been exposed to the drug for more than one year and approximately 600 for over two years. In controlled trials, 2249 subjects, who included normal volunteers and patients with hypertension and congestive heart failure, have received enalapril alone or concomitantly with hydrochlorothiazide or other antihypertensive agents. There have been no deaths attributed to enalapril. The incidence of serious adverse experiences in controlled trials was similar to placebo, and was not higher in the elderly. The incidence of adverse experiences was not dose-related. Drug discontinuation due to adverse experiences was 3.5%, similar to placebo, and approximately half that of control drugs. Serious laboratory adverse experiences were rare. Enalapril attenuated the adverse metabolic effects of hydrochlorothiazide, particularly hypokalaemia. Skin rash occurred in approximately 1.0% of patients. One case of transient taste loss occurred on enalapril, and one on enalapril in combination with hydrochlorothiazide. Neutropenia and agranulocytosis were not encountered. Mean white blood cell counts did not change overall. Most patients (approximately equal to 80%) show no change or an improvement in renal function on enalapril. Discontinuation of concomitant hydrochlorothiazide usually normalized renal function. Enalapril is well tolerated in renal insufficiency. Azotaemia may occur in bilateral renovascular hypertension. Proteinuria was rarely seen and often improved on enalapril. Compassionate use protocols have been available to patients either resistant or intolerant to captopril. Of 68 patients admitted for captopril-related skin rashes, only five recurred on enalapril.(ABSTRACT TRUNCATED AT 250 WORDS)