He served as leader of South Korea's former ruling Uri Party and health minister. He had long suffered symptoms of harsh torture for his democratization efforts decades ago. He was repeatedly imprisoned for leading protests against military dictatorships in the 1970s while studying at Seoul National University, and the 1980s.
He was diagnosed with Parkinson's disease years ago, apparently attributable to torture at that time.
Kim was first elected as lawmaker in 1996 for a four-year tenure and served two more terms.
He had long played a pivotal role in South Korea's liberal bloc.
He received the Robert F. Kennedy Human Rights Award together with his wife, In Jae-keun, in 1987.
He is survived by In, a son and a daughter.