Peak expiratory flow rate (PEFR) gives the measure of maximal expiratory flow rate sustained by a subject for at least 10 milliseconds expressed in Liter per minute. It measures the level of airway obstruction. PEFR varies in an individual according to the age, sex and anthropometric variables. The present study was undertaken to assesses and correlate the Body mass index and Peak expiratory flow rate in overweight and underweight male and female young adult subjects. A total number of 40 healthy young adults aged between 18-26 years were included in this study. PEFR was measured in standing position. BMI was calculated. PEFR values were low in females as compared to male subjects and it was highly significant. PEFR values were less in low BMI and overweight subjects as compared to normal BMI subjects and it was highly significant. PEFR was low in these subjects as compared to subjects having normal BMI. Early identification of risk individuals prior to onset of disease is imperative in our developing country. It is necessary to have a good physical activity and proper nutrition in young adults to avoid future respiratory problems.