Introduction: The value of FEF 25%75% has been both praised and condemned. The test has been recommended by Leuallen E. et al as an early index of airway obstruction. According to Gilbert R. et al. a normal value has poor specificity. It has been suggested by Voter K.Z that obstruction in peripheral airways can be discriminated from that in larger airways by a disproportionate decrease in FEF 25%75% compared to FEV1. Methodology: First, case history is taken with special emphasis on personal habits. Then secondly the physical examination including the measurement of height and weight. All the tests are done at the same time of the day to avoid possible diurnal variation. Subject is allowed to sit comfortably on the stool. Instructions are given about the tests. Results: Nonsmokers with normal weight is having mean FEF of 71.13 with a standard deviation of 20.15 and nonsmokers with over weight the mean is 74.86 and standard deviation is 18.83. Conclusion: The effect of smoking on FEF is more affected in overweight group of subjects than the normal weight group of subjects.

Keywords: FEF; Smoking; Overweight.