One day surgery in children has been practiced for last 10 years in this institution. This study is to examine its safety and effectiveness for patients younger than 15 years old treated at the Department of Pediatric Surgery, Asan Medical Center, from September. 1996 to December, 2005. A total of 3,709 patients, 37 % of the total pediatric operations, are included in this retrospective study. The most prevalent ages were between 1 and 3 years olds (1,199 patients). Twenty patients were younger than 6 months, and they all had one day surgery safely. Operations were herniorrhaphy in 3,126 patients,followed by excisional biopsy, chemoport removal, and OK 432 injection. There were 12 cases (0.32 %) of unplanned admissions, 7 occurred within 6 months of one day surgery. Perioperative fever was the most common cause of admission in 4 cases. The related conditions of unplanned admission were bleeding in 2 cases and radical surgery in 2. One day surgery in this institution was easily accessible and safe. This is to the result of appropriate selection of patients, cooperation with anesthesiologists, adequate control of postoperative pain, and home care programs.