<p>Angiotensin-converting enzyme (ACE) activity in serum and insertion/deletion (I/D) polymorphism have been associated to cardiovascular disease in several studies. Objective. To find a relationship between ACE activity and I/D polymorphism in the enzyme gene in patients with coronary obstruction revealed by angiography. Materials and methods. Sample comprised patients attending a hemodynamics center in Quindío in need of a coronary angiography. ACE activity was measured by electrophotometry and the I/D genotype determined by polymerase chain reaction. Results. 542 patients were divided into two groups: individuals with coronary obstruction higher than or equal to 50% (OC≥50) and individuals with coronary obstruction less than 50% (CO<50%). Serum ACE activity in the global population was higher in individuals with DD polymorphism, followed by ID and II with significant differences. A similar pattern was shown in both study groups but without significant differences, although enzyme activity was always higher in individuals with OC≥50% compared with patients with OC<50%. ID genotype was the most frequent in both groups. No differences were found in allele and genotype frequencies in the study groups. Conclusions. Significant differences in ACE activity were found<br />according to genotype. Our study did not find any relationship between ACE activity, I/D polymorphisms and coronary obstruction.</p><p><br />Key words: angiotensin-converting enzyme, coronary obstruction, ID polymorphism, angiotensin.</p>