In his latest video, John Oliver takes on the problem of doping in professional sports. In recent years, many preeminent athletes, including Lance Armstrong, Alex Rodriguez, and most recently Maria Sharapova, have been caught using a veritable pantry of banned substances to enhance their performances. And despite the costly consequences and widespread condemnation of the athletes after their doping was revealed, doping in sports remains a major problem.

It’s an even bigger issue this year with the Olympics in Rio de Janeiro only a few weeks away. Just a few days ago, Brazil’s anti-doping lab that was set up for the Olympics was shut down by the World Anti-Doping Agency because it didn’t conform to WADA standards.

Dedicated anti-doping testing facilities are now a part of international athletic competitions. Before the 2012 Olympics, the International Olympic Committee (IOC) unveiled a 24/7 anti-doping facility.

Oliver’s piece focuses primarily on Russia’s issues with doping, which came to a head when their entire track and field team was banned from the summer Olympics.