Introduction: The incidence of diabetes mellitus is increasing tremendously throughout the world especially in developing countries. This disease affects various organs like eyes, nerves, kidneys and heart. Pulmonary complications of diabetes mellitus (DM) have been poorly characterized. Moreover, the duration of glycemic control have varied impact on the pulmonary function. Aims and objectives: To study the effect of DM on PEFR and its relationship with duration of the disease. Material and method: The study was carried out in the department of physiology M.G.M Medical College Aurangabad. Total 90 subjects were included in the studies &were grouped in 3 groups of 30 subject in each respectively. Group I consist of 30 age and socio-economically matched apparently healthy non diabetic subject were randomly selected from the OPD mainly the relatives of patients. Group II consist of 30 type 2 DM patients with the duration of 5 to 10 years of disease. Group III consist of 30 type 2 diabetic patients with duration of 10 to 20 years of disease. The PEFR of all the subjects were measured by spirowin, a computerized spirometer. Blood samples were taken for heamatologicl and biochemical parameters. The data were analysed by one way ANOVA, unpaired students “t” and Pearsons correlation coefficient tests. Results: The mean percentage of predicted values of PEFR in non diabetic male was within normal range. But it was significantly (p <0.001) lower in both the groups of type 2 diabetic male compared to those of non diabetic male. PEFR was lower in the patients of longer duration as compared to those of shorter duration. Conclusion: PEFR is lower in type2 diabetic male and is inversely related to the duration of the disease.