Angiotensin converting enzyme (ACE) converts angiotensin I to angiotensin II and inactive bradykinin. Several studies carried out in our laboratory have consistently identified three isoforms of ACE, at 65, 90 and 190 kDa, with the 90-kDa isoform being a possible genetic marker of hypertension. Based on these observations and the fact that nutritional stunting can be associated with hypertension, we have investigated the expression and activity of ACE in stunted children and its association with blood pressure (BP) levels and nutritional state. Sixty children aged 2-7 years were selected for this study. A urine sample was collected from each child. Angiotensin converting enzyme activity was evaluated using two different substrates, and ACE expression was detected by Western blotting. Our results show that nutritional stunting is associated with high ACE activity in childhood and that adjustment by gender does not modify the strength of this association. A greater percentage of stunted children had increased BP levels, and this clinical parameter was inversely correlated with anthropometric indicators. A greater urinary protein expression of the three ACE isoforms was observed in the group of children with growth stunting. Our findings suggest that the reported high risk of hypertension in stunted adolescents and adults are, at least partly, associated with abnormalities in the renin-angiotensin system.