Fosinopril is a phosphinic acid prodrug which, after oral administration, undergoes rapid hydrolysis to its active diacid, the angiotensin converting enzyme (ACE) inhibitor fosinoprilat. Unlike other ACE inhibitors, fosinoprilat has a compensatory dual route of elimination and is cleared by the liver and kidneys. Thus, in patients with diminished renal function increased hepatic clearance of fosinoprilat is noted and, similarly, in patients with diminished hepatic function increased renal clearance seems to occur. Because of this compensatory elimination, fosinopril therapy for all patients can begin with the same recommended dosage. Fosinopril 10 to 40mg administered once daily is an effective antihypertensive regimen that has shown efficacy similar to that of enalapril 5 to 10 mg/day, propranolol 80 to 160 mg/day, hydrochlorothiazide 25 to 50 mg/day and sustained release nifedipine 40 mg/day in preliminary clinical trials. Generally, fosinopril is well tolerated and adverse events associated with the drug are usually mild and similar to those associated with other ACE inhibitors. Thus, fosinopril appears to be a useful alternative to certain 'established' agents used for treating patients with essential hypertension.