| 2004~ | Division Director, Division of Ped. Hem./Onc./BMT, University of Ulsan College of Medicine and Asan Medical Center, Seoul, Korea |
| 1998~ | Professor of Pediatrics, University of Ulsan, College of Medicine & Asan Medical Center, Seoul, Korea |
| 1995-1998 | Associate Professor of Pediatrics, University of Ulsan, College of Medicine and Asan Medical Center, Seoul, Korea |
| 1992-1994 | Associate Professor of Pediatrics, CNU, College of Medicine, Daejon, Korea |
| 1988-1992 | Assistant Professor of Pediatrics, CNU, College of Medicine, Daejon, Korea |
| 1986-1988 | Instructor of Pediatrics, Chungnam National University (CNU), College of Medicine, Daejon, Korea |
| 1985-1986 | Chief, Department of Pediatrics, Seobu General Hospital, Seoul, Korea |
| 1977-1980 | Medical Officer, Korean Navy |