Type-2 diabetes mellitus (T2DM) is a chronic disorder characterized by a varying range of predominant insulin resistance with relative insulin deficiency, to predominant insulin secretory defect with or without insulin resistance. Familial clustering as well as epidemiological studies has shown that genetic factors play a role in the development and progression of the disease. Among the genetic factors found to be associated with development of T2DM is the angiotensin-I converting enzyme (ACE) gene, which is located on chromosome 17q23. This study was conducted to study the association between ACE gene insertion/deletion (I/D) polymorphism and T2DM in a Lebanese diabetic cohort. Fifty-one patients with T2DM and 40 control subjects from different parts of Lebanon underwent genotyping for the ACE I/D, which was performed by PCR using specific primers. Chi-square and analysis of variance (ANOVA) were used for association studies and to assess the differences in the values among the groups. The distribution of the genotypes in the patients was as follows: 15/51 (29.4%) were homozygous for deletion allele (DD genotype), 24/51 (47.1%) were heterozygous (ID genotype), and 12/51 (23.5%) were homozygous for insertion allele (II genotype). Among the control subjects, 16/40 (40%) were homozygous for deletion (DD genotype), 13/40 (32.5%) were heterozygous (ID genotype), and 11/40 (27.5%) were homozygous for insertion (II genotype). The prevalence of the D-allele in T2DM patients (52.9%) was not significantly different from that in the controls (56.3%). Thus, ACE I/D dimorphism cannot be considered a risk factor for T2DM in the Lebanese population.