Background: Cardiorespiratory fitness (CRF) is not only objective measure of habitual physical activity, but also a useful diagnostic and prognostic health indicator for patients in clinical settings. CRF is a strong and independent predictor of cardiovascular disease mortality. Low CRF in young adults has emerged as an important factor for developing cardiovascular comorbidities later in middle age. Aims: To determine the peak oxygen consumption (VO2max) by Queen’s college step test in young male subjects. To study the relation between body mass index and VO2max. Methods: One hundred young healthy male subjects in the age group of 18 to 25 years were included in this study group. Body mass index (BMI) was measured using standard calibrated instruments. VO2max was assessed by following the protocol of Queen’s College Step Test (QCT). Results: Data was statistically analysed by using Pearson’s correlation. There was a significant negative correlation between Body mass index and VO2max (ml/kg/min) (r= -0.418, p<0.01). Conclusion: The results suggest excessive amount of body fat exerts an unfavourable burden on cardiac function and oxygen uptake by working muscles. In our study BMI has significant negative correlation with VO2max and can be used in clinical settings to estimate cardiorespiratory fitness as it is a rapid and inexpensive method.