On behalf of the Korean Society of Obstetrics and Gynecology, we are extremely honored to welcome lots of esteemed professors and promising young colleagues to share valuable experiences at the 21st Seoul International Symposium held in Seoul, Korea on Sept.24, 2016. The scientific program consists of diverse presentations by distinguished speakers, presenting on updated topics in the clinical fields and basic research studies to enhance further medical development. Various subjects in Obstetrics and Gynecology will be discussed and debated, including issues in gynecologic oncology, reproductive endocrinology, maternal-fetal medicine and general gynecology. In addition, in this year, both Prof. Tsung-Hsien Su from Taiwan and Prof. Yuji Hiramatsu from Japan will be new Honorary members of KSOG. The purpose of this symposium is to provide great opportunities to share different opinions on specific subjects and current issues. It will also be an opportunity for our younger colleagues to participate in these high-level discussions and a chance to receive answers to open questions. Thus, your participation will be a crucial part to form a fruitful platform in order to share our knowledge and build a broad base of therapy features for our patients. We hope that all of participants would enjoy our sessions and have a wonderful memory in Korea.