Dr. Kobayashi was born in 1927 in Tokyo. After graduating from University of Tokyo School of Medicine in 1954, Professor Kobayashi studied overseas in the United States and England. In 1970, he became a full professor at the University of Tokyo School of Medicine. In 1980, he was appointed chairman of the International Pediatrics Association, and in 1984 was named the first Chairman of the National Children's Hospital Research Center. He became Professor Emeritus at the University of Tokyo in 1988, and in 1996 President Emeritus of National Children's Hospital. In that same year, he was also named Professor at Konan Women's University and Director of the Child Research Net.
Professor Kobayashi has served in senior posts on numerous academic associations and on governmental committees; as a member of the Ad Hoc Council for Education (Prime Minister), Central Committee for Children's Welfare (Minister of Health and Welfare), Central Drug Committee (Minister of Health and Welfare), Committee for Population Issues (Minister of Health and Welfare), director of the Japan Pediatrics Association, and director/auditor of the Japan Society of Allergology.
In 1984, he received the Award for Distinguished Achievement from the Japan Medical Association, in 1985 the Mainichi Cultural Award, and in 1986 he was honored by the International Pediatrics Association.
In addition to editing and contributing to four pediatrics textbooks, his many publications include New Survey of Pediatric Medicine (Vol. 41 of 90 vols.), Human Science (Nakayama Shoten, for which he received the Mainichi Culture Award), Children are the Future (Media Science Co., small paperback edition by Iwanami Contemporary Library), Children: Voyagers to the Future (Tokyo Shoten), and Childcare: Where Raising and Growing Meet (PHP Research Center).