This bioequivalence study was supported by Laboratorios Vita S.A (Barcelona). To study the existence of differences between sexes in the pharmacokinetic and pharmacodynamic of enalapril. A bioequivalence phase 1 clinical trial to compare two formulations of enalapril was carried out in twenty-four healthy volunteers (12 men and 12 women). Enalaprilat concentrations, plasma activity of ACE, and systolic and diastolic arterial pressure were determined. Basal activity of ACE and the maximum ACE inhibition were significantly smaller in women. No significant differences in the drug concentration required to produce 50% of Emax were observed. Women had lower systolic arterial pressures and ACE activities than men at any time, even when the maximum inhibition of the ACE activity was attained. Women at the follicular phase had a minimum activity of ACE significantly inferior than men. Healthy women had lower systolic arterial pressures and ACE activities than men.