In an open, crossover study, the pharmacokinetic and pharmacodynamic profiles of lisinopril and enalapril, administered alone and in combination with propranolol, were evaluated in 12 volunteers. The maximum serum concentration (Cmax) of lisinopril and time to reach maximum concentration (Tmax) were 64 +/- 16 ng/ml and 7.5 +/- 1.5 h, respectively. The area under the serum curve (AUC) was 916 +/- 239 h. ng/ml. The Cmax of enalaprilat (89 +/- 34 ng/ml) was greater than that of lisinopril whilst Tmax was shorter (4.3 +/- 1.7 h) and AUC smaller (718 +/- 17 h.ng/ml) (P less than 0.01). Renal clearance of drug 48 h post-dosing showed that enalaprilat (164 +/- 38 ml/min) was cleared from plasma significantly more rapidly than lisinopril (82 +/- 16 ml/min) (P less than 0.001). Mean supine blood pressure decreased significantly with all treatments, as did heart rate. No significant changes were observed in either the serum concentrations or the urinary outputs of these ACE inhibitors following combination with propranolol, apart from a greater variability of Cmax after addition of propranolol to enalapril compared with lisinopril in combination.