This study was performed to identify the factors influencing on awareness levels of medical service in ambulatory surgery patients in a tertiary health care in Korea. Data were surveyed using interview and questionnaires by 166 outpatients who visited a general hospital which was located in Chungnam area from January 13 to February 26, 2015. General characteristics and factors related to awareness levels of medical service were analyzed with descriptive statistics by frequency and percentage. factors related to awareness levels according to general characteristics were measured by t or ANOVA. Factors Influencing on ambulatory surgery outpatients were performed by multiple regression analysis. The results of this study are as follows. Firstly, for the subject’s gender, male with 51.2% revealed higher rate than female with 48.8%. Secondly, for religion, the proportion of christianity(28.3%) was a higher rate than the proportion(20.5%) of buddihism. Thirdly, in the factor related to awareness levels of Received(November 16, 2015), Review request(November 17, 2015), Review Result(1st: December 04, 2015, 2nd: December 30, 2015) Accepted(January 08, 2016), Published(January 31, 2016) 32588, Dept. of Medical Information, Kongju National University. 56 Gongjudaehak-ro, Gongju-si, Chungnam, Korea email : leesr@kongju.ac.kr Factors Influencing on Awareness Levels of Medical Service in Ambulatory Surgery Patients in A Tertiary Health Care Copyright c 2016 HSST 110 medical service, outpatients who had an experience with hospitalizing, there was significant difference in regard to the reliability of medical service(t=0.584, p<.05). Fourthly, multiple regression analysis revealed that their age and education affected the perception of ambulatory surgery (p<.05). In conclusion, in order to increase the rate of ambulatory surgery, it is necessary to give information about the advantages of ambulatory surgery and preoperative education.