Walter Payton died from complications from an autoimmune liver disease called primary sclerosing cholangitis and cholangiocarcinoma in November 1999. The latter illness is bile duct cancer, which doctors believe came from his liver disease.
Walter Payton was a famous running back for the NFL's Chicago Bears. He retired in 1987 and was, at the time, the all-time leading rusher in the league's history. Walter Payton used a variety of prescription medications during his days on the field to deal with the pain from injuries and general football soreness. He continued using those pills after the retired.
A book called "Sweetness: The Enigmatic Life of Walter Payton," by Jeff Pearlman illustrated the amount of pills Payton took on a regular basis. Payton announced that he had the liver disease in February of 1999, several months before he met his demise. In his remaining months, he advocated strongly for organ donation, despite the fact that his own disease was too far advanced to improve with an organ transplant.
The NFL honored Walter Payton when he died. Teams held ceremonies during the week he died to commemorate him and his accomplishments. The Chicago Bears wore his 34 jersey number as patches on their jerseys.