Peak expiratory flow rate (PEFR) is a measure of ventilatory capacity measured by peak flow meter. It is regarded as a basic physiological parameter for the diagnosis, follow up and treatment of patients with respiratory illnesses such as asthma, chronic bronchitis, and emphysema. This study establishes the relationship of PEFR with age and BMI in healthy adult males (N=300) of Kumaon region of Uttarakhand. Overall, the mean PEFR is 478.37+68.14. The age is significantly affecting the PEFR unlike BMI. Age as an independent predictor predicts the 72.3% variability (R is 72.3%)in PEFR while BMI > 23 as an independent predictor predicts only 1.4% variability (R² is 0.014) .PEFR declines with advancing age due to degenerative changes in musculoskeletal system leading to decrease in respiratory muscle strength. PEFR shows some decline with high BMI in elderly age group.