4 × 400 metres Relay, Men

The United States had swept the medals in the 400 metre flat race and had by far the fastest team. With hand-offs less critical than in the 4x100 relay, there seemed no way for them to lose the gold medal. In the final, they used their 400 medalists, LaShawn Merritt, Jeremy Wariner, and David Neville, with 400 hurdle gold medalist Angelo Taylor running the second leg. Merritt led off with a 44.35 leg that put the US in the lead by over a second on Belgium. Taylor took over and maintained that lead, Belgium still in second at the second hand-off. Neville ran the third leg for the Americans and increased the lead over Belgium slightly to 1.28 seconds as he handed the baton to Wariner. Wariner ran 43.18 on the anchor to win the gold medal for the Americans by over 25 metres. Belgium was still in second at the bell, but they had placed their three best runners up front and they were passed by four teams on the final lap, eventually finishing fifth. The Bahamas and Russia closed quickly on the final leg to get the silver and bronze medals, respectively.

That was how the event and the results seemed to have ended. In 2015, however, the IOC began re-testing samples from the 2008 Beijing and 2012 London Olympics, using newer, more advanced testing techniques, in an effort to find those who had used performance enhancing drugs (PEDs), but in whom it could not be detected at the time of those Olympics. This was one of the many events affected.

In September 2016 Russian Denis Alekseyev was disqualified for a positive re-test for turinabol (dehydrochloromethyltestosterone). Alekseyev had also competed in the 400 metres but did not advance out of the first round. In the relay, his positive test caused the Russian team to be disqualified, with the bronze medal re-assigned to Great Britain.