The Minnesota Vikings drafted Stringer in the first round (24th pick overall) of the 1995 NFL Draft, and he played for the Vikings from 1995 to 2000. He was a standout on the offensive line, earning Pro Bowl honors in what turned out to be his final season in 2000. In six NFL seasons, he played in 93 regular season games and started 91 of them. As a professional player, Stringer was well-liked inside the locker room and out; after a Vikings game, he stopped to help a fan change a flat tire, and he impulsively signed over his Pro Bowl appearance check to a youth football program in his hometown of Warren.
He suffered from heat stroke on the second day of the Vikings 2001 preseason training camp, and died as a result of complications on August 1, 2001. Stringer was unable to complete the first practice session, held the morning of July 30, due to exhaustion, and did not participate in that day's afternoon session, but he vowed to return the next day to complete the morning session, which was conducted in full pads. Although he vomited three times, he did complete the morning practice session on July 31, which lasted 21⁄2 hours, but walked to an air-conditioned shelter after the session, where he became weak and dizzy. Offensive line coach Mike Tice stated that he had not witnessed Stringer vomiting, and that Stringer did not exhibit any symptoms of heat-related illness. At 11:30 AM, when practice ended, the heat index had reached 99; the heat index peaked later that day at 110 with a high temperature of 90°F.
When he was taken to Immanuel St. Joseph's–Mayo Health System hospital, his body temperature was 108°F upon arrival. Stringer was unconscious from the time he was admitted until his death at 1:50 AM on August 1. An autopsy confirmed that Stringer died from organ failure resulting from heat stroke.
The Minnesota state Occupational Safety and Health Administration (MNOSHA) investigated Stringer's death, and cleared the Vikings of responsibility on November 1, 2001. The Vice President of the Vikings, Mike Kelly, met with MNOSHA officials along with the team's trainer and equipment manager. However, under the governing labor laws, the Vikings would only be held liable if it was proven they were negligent or had inflicted intentional harm. Although the autopsy confirmed that Stringer was not taking supplements, the Vikings began preparing a defense to a planned lawsuit by announcing that Stringer's locker was full of dietary supplements in November 2001, including some that contained ephedra.
Stringer's widow filed a wrongful death lawsuit against the team and trainers in February 2002. The trainers were granted summary judgment for immunity, which was upheld on initial appeal as well as a second appeal to the Supreme Court of Minnesota. Parts of her lawsuit were later thrown out; another suit against the NFL was filed in July 2003 and settled in January 2009. The only disclosed term of the settlement is that the NFL will support efforts to create a heat illness prevention program. His widow also brought a lawsuit against Riddell Inc., the manufacturer of Stringer's pads and helmet. In July 2009, a federal judge determined that Riddell had a duty to inform Stringer that their equipment could contribute to heat injuries. A district court judge then ordered a jury trial regarding the matter.
Stringer's death brought about major changes regarding heat stroke prevention throughout the NFL. His death also addressed complications of pressuring players to "bulk up" to well over 300 pounds. Stringer, who at the time of his death was 6'4" and weighed 335 pounds, was at the lowest weight he had ever been in his pro career. Many professional football teams now train in light color uniforms, water and shade are made readily available, and a team doctor is at practice sessions at all times.