A comparative study to assess the effectiveness of OSCE vs. Traditional method (essay type) in terms of knowledge regarding ABG analysis among B.sc Nursing. The present study aimed to assess 1)To assess and compare OSCE v/s Traditional method (essay type) in terms of knowledge regarding ABG analysis among B.sc nursing students. 2) To determine the association of level of knowledge regarding ABG analysis with their selected demographic variables. 3) To determine the association of level of satisfaction regarding ABG analysis with their selected demographic variables. The research approach for the study was non– experimental research approach with descriptive comparative research design. The study conducted in the Maharishi Markandeshwer College of nursing Mullana, Ambala. The knowledge questionnaire for Traditional method and different stations for OSCE was used to collect data and rating scale was used for checking the level of satisfaction. Data obtained were analyzed using descriptive and inferential statistics Personal variables revealed that for both the OSCE and the tradition method majority of student were in the age group of 19–21 i.e. 70% for OSCE an 60% for Traditional. Majority of students are females i.e. for OSCE 72.5% and Traditional 70%. Majority of students resides in hostel i.e. for OSCE 70% and Traditional 72.5%.Majority of student were having the previous knowledge regarding ABG analysis. Majority of students lies in the category of last year percentage 50–75% i.e. for OSCE 77.5% and for tradition is 80%. Level of knowledge of B.SC nursing students towards OSCE is good (62%) and in the tradition is average (42%). Majority of students i.e. 65% agree with OSCE method and for Traditional it is 30%. Mean standard deviation for OSCE is 4.8± 2.28 and for Traditional t is 2.8±1.45. The mean scores found with the OSCE method (mean=4.8) and the score by Traditional method (mean=2.8) and there has been a significant difference between the scores (z=4.04). It is concluded that OSCE is considered as an effective method for assessing knowledge and evaluation than Traditional method.