ABSTRACT Background : In the emergency setting agreement between venous and arterial blood gas parameters and their clinically acceptable limits are yet to be clearly defined . As per the available data, venous pH and arterial pH have good correlation to be used in clinical practice. pH, pCo2 , BE and K+ parameters and their correlation with one other has been limited in few settings and clinical conditions like shock , mixed acid base disorders, etc .The present study is being undertaken to determine agreement between arterial and venous blood gas values in patients with diverse etiology . Aims and Objectives : To determine agreement between simultaneously obtained ABG and CVBG values of pH, pCo2, BE an K+ levels in patients presenting to emergency department with diverse etiology. Study Design and Settings : Prospective observational study undertaken in emergency and critical care units . Material and Methods : A total of 40 samples were collected from patients , presenting to emergency department with diverse pathological conditions and deemed by treating physician to require an ABG analysis . Arterial blood was collected from radial or femoral artery and simultaneously central venous blood sample was drawn from the patient. Comparison of mean values was done using t – test , correlation and agreement was tested using Pearson's Correlation and Bland Altman Analysis. Statistical methods : The data collected was stored confidentially in Microsoft Excel sheet in the computer under password guidance and statistical analysis was done using SPSS software -version 21. Results : In the present study 65% -(26) males 35% -(14) females .Majority -16( 40%) of the patients fall in the age group of 31-60 yrs . In the study distribution of patients as per the etiology showed that 32.5 % were poisoning patients ,23 % had metabolic disorders ,and the rest had renal –18%,cardiovascular - 10%, pulmonary -5% and hepatic - 5 % disorders respectively .As per the study results , mean values of pH , pCo2, BE showed close agreement between arterial and central venous samples (p <.0001). The mean difference between arterial and central venous blood gas values for pH, pCo2, BE and K+ was – 0.11, 2.26, 2.08, 1.06 respectively. Bland-Altman plots for agreement of pH, pCo2, BE and showed good correlation - r values being 0.94, 0.96 ,0.97 respectively.The K+ levels of arterial samples has poor agreement and could not be compared with central venous values – p = 0.375 , r = -0.14 respectively . Conclusions : The arterial pH, pCo2 and BE values correlated well with central venous blood gas values , but the K+ values were found to have poor correlation.