Background: Estimation of blood gas values is vital in critically ill patients. The arterial blood gas estimation has some complications. Venous blood gas values can substitute the arterial blood values. This study was undertaken to compare the arterial and venous blood gas values in emergency care setting. Materials and Methods: A cross sectional study was conducted in Emergency Department of Basaveshwara Medical College and Hospital, Chitradurga among 85 patients. The samples were obtained from the artery and central
vein of the patients with 2 mins apart. The sample was sent to the laboratory for estimation of blood gases including pH, pCO2, BE and K+. Results: This study had shown that, pH, pCO2, BE and K+ were correlated significantly but there is slight difference in the K+ between the Arterial and venous blood samples. The central venous sample had shown to have less potassium than the arterial blood. The pH, pCO2 and BE values can be explained physiologically where the pH will be slightly lesser in venous samples and pCO2 will be higher. Conclusion: This study concludes that, there was a good correlation between the arterial and venous pH, pCO2, BE and K+ values.