The present study evaluated the controversial role of angiotensin-converting enzyme (ACE) I/D polymorphism in patients with hypertrophic cardiomyopathy (HCM). Two hundred and eleven unrelated HCM patients (138 sporadic and 73 familial) and 203 age and sex-matched healthy volunteers were included. The ACE DD genotype was higher in HCM patients (P=0.049) and significantly more common in the sporadic HCM group (P=0.0001). Although the distribution of ACE I/D genotype in the control group was in Hardy–Weinberg equilibrium (P=0.778), it was not so in HCM patients (P=0.0010). Among the patients with known sarcomeric mutation, the distribution of D allele was observed to be higher among those having mutations in TNNT2 and MYH7 (P=0.0476). Similar to other studies undertaken in different populations, there was no significant effect of the ACE I/D genotype observed on HCM phenotypic characterization in the present cohort. ACE I/D allelotyping probably plays a contributing role in initiation of HCM phenotype synergistically with the causative pathogenic sarcomeric mutation, rather than directly influencing variable disease expressivity.