Abstract: This study aimed to investigate on catalase activity and genetic polymorphism in diabetes patients, the blood sample were collected from 20 type II diabetic patients attending the outpatient department and admitted to the RMMCH. The age of patients ranged from 40-65 years of both sexes. Reactive oxygen species generated by hyperglycemia modify structure and function of lipids, proteins and other molecules. This study was undertaken to investigate the association between gene polymorphisms of selected antioxidant enzymes. The 20 type 2 diabetes mellitus patients were analyzed for SNP in catalase gene. Restricted fragment length polymorphism studies showed 80% of the patients were TT genotype and 20% were of heterozygous genotype. No AA genotype was observed in our group of study. Observed that patients with T allele had significantly lower fasting plasma glucose, RBC catalase activity and HbA1c where as heterozygous had higher FPG, RBC catalase activity high and HbA1c. It is suggestive of possible association of heterozygocity with poor glycemic control and high catalase activity. It has been observed that the level of enzyme was found to be significantly high in heterozygous group. High (concentration) activity may be secondary to high oxidative stress as a result of poor glycemic control. In heterozygous patients the association of high catalase activity with this SNP should be carefully considered because early study has reported that there is no statistically significant difficult association of CAT alleles and this activity.