Peroxisome proliferator activated receptor-gamma (PPAR-gamma) and transcription factor 7-like 2 (TCF7L2) gene polymorphisms. are some of the genetic variants that are commonly held responsible for the genetic pathogenesis of type 2 Diabetes Mellitus (T2DM),In this study the genetic polymorphisms of TCF7L2 and PPAR-gamma genes in affected siblings of. families with rich diabetic history and their unaffected siblings who are thought to be resistant to diabetes development were evaluated: 28 T2DM patient group (Group I), 27 siblings who still have not developed T2DM 10 years after the earliest T2DM diagnosis age in the family (Group 2) and 20 healthy individuals who do not have T2DM and no history in the first degree relatives (Group 3). PPAR-gamma Prol2Ala and TCF7L2 gene polymorphisms (rsI2255372 and rs7903146) were searched for in these groups. Moreover oral glucose tests and insulin secreting abilities of individuals in group 2 were investigated. PPAR-gamma Pr612Ala gene polymorphism was not detected in any of the patients in our study group. There were no significant differences between group 1 and 2 regarding TCF7L2 gene polymorphism genotyping. TT genotype and T allele ratio was less in group 3 when compared to other groups but this was not statistically significant As a result, it was Observed that PPAR-gamma Prol2Ala polymorphisms do not have an affect on T2DM development. However TCF7L2 gene polymorphisms, although not a strong determinant, may play a role in diabetes along. with other genetic and environmental factors.