Title: Modified Harvard step test (HST) is fairly accurate and reliable method for calculating Physical Fitness Index (PFI).Body mass index affect cardiorespiratory endurance and pulmonary function. In Present study assess body mass index affect cardiac and pulmonary fitness. Method: In study, Forty-nine healthy adults aged 25-35 years performed Harvard step test for calculating physical fitness index. For Pulmonary function performed pulmonary function test. Results: Person’s correlation test was used to Correlated body mass index to physical fitness index and pulmonary function test. Conclusion: Body mass index was negative correlated to physical fitness index and pulmonary function test.