Perindopril is a non-sulphydryl angiotensin converting enzyme (ACE) inhibitor which requires hydrolysis to its active metabolite, perindoprilat, to produce its effects. Ten cirrhotic patients with mild to severe disease were studied after oral administration of a single 8 mg dose of perindopril as its tert-butylamine salt. Compared with a historical control group of young healthy volunteers receiving the same single oral dose of perindopril, mean AUC values of the prodrug perindopril were double in patients with liver cirrhosis (602 +/- 294 s.d. ng ml-1 h vs 266 +/- 70 s.d. ng ml-1 h) whereas the mean AUC of perindoprilat was found to be similar (134 +/- 139 ng ml-1 h vs 120 +/- 29 ng ml-1 h). The partial metabolic clearance of perindopril to perindoprilat was much lower in the cirrhotics (26 +/- 12 ml min-1 vs 58 +/- 22 ml min-1). The maximum inhibition of plasma ACE activity measured in the cirrhotic patients (87.5 +/- 5.1%) was comparable with that previously reported with perindopril in patients with mild hepatic impairment as well as in patients with essential hypertension. We suggest that liver cirrhosis may be associated with imparied deesterification of perindopril to its active metabolite perindoprilat but that no dosage adjustment of perindopril is required in cirrhotic patients.