Introduction. The aim of the current study was to evaluate the role of angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism on the prediction of type 2 diabetes in two ethnic populations from Jerba Island, Tunisia. Methods. In this study, we analysed the genotypic and the allelic distributions of the ACE I/D polymorphism and conducted a case/control association study between healthy normoglycaemic controls and diabetic patients in the two studied groups. ACE gene polymorphism was analysed by polymerase chain reaction in 272 individuals consisting of 172 diabetic subjects and 100 controls. Results. The genotype frequencies for DD, ID and II were 75.50%, 19.60% and 4.89% in Arabs and 76.66%, 16.66% and 6.67% in Berbers, respectively, in the case group, and 42.85%, 35.71% and 21.43% in Arabs and 57.50%, 22.50% and 20.00% in Berbers, respectively, in the control group. The DD frequency was significantly higher in the case group than in the control group (p<0.001), suggesting that the DD genotype is associated with an increased susceptibility to type 2 diabetes in our study populations. Conclusions. The current investigation provides new evidence regarding the role of the ACE I/D polymorphism in the pathogenesis of type 2 diabetes in Jerbian populations. Furthermore, it underlines the importance of ethnicity, which should be considered in all studies aiming to test the genetic effects on the susceptibility to type 2 diabetes.