Professor Han was Chairman of the Board of Directors and was a president of Korea transplant society. Now he is a councilor of International Pancreas and Islet Transplant Association(IPITA). He has presented invited papers/lecture at the Congress of the Asian Society of Transplantation and the World Transplant Congress. Professor Han has been involved in a number of clinical trials, and has publicized 411 articles, 18 book chapters, and 2 editor of books.
In 1992, Professor Han carried out the first successful cadaveric pancreas transplant and living donor pancreas transplant in Korea. Up to Dec 2020 he has done more than 6,000 renal transplants and 480 pancreas transplants including 21 living donor Pancreas Transplantation.