A single dose complete crossover study of a combined dosage form of enalapril maleate (10 mg) and hydrochlorthiazide (25 mg) marketed in India was carried out in 12 healthy male volunteers. The formulation was compared with a standard formulation of enalapril maleate (10 mg) and hydrochlorthiazide (25 mg). Plasma were analysed for enalapril maleate by using the indirect method of Angiotensin I radioimmunoassay (RIA) method. Hydrochlorthiazide in plasma was analysed by High Performance Liquid Chromatography (HPLC). Pharmacokinetic parameters such as C(max), T(max), AUC0-24, AUC(0-∞) and T( 1/2 ) were determined and subjected to statistical analysis. The data obtained was compared with the data obtained from the study conducted by administering enalapril maleate alone. The study showed that hydrochlorthiazide did not alter the pharmacokinetics of enalapril maleate. The study showed no undesirable pharmacokinetic interaction between the two drugs.