Listed below are five of the most notable cases of doping in the UFC over the past couple of years.
- Brock Lesnar: Was penalized in 2016 after he tested positive for anti-estrogen drugs before and after his 2016 co-main match in UFC 200. Re-applied for a drug clearance in 2018; in the meantime, Lesnar has returned to WWE Raw while awaiting the all-clear to fight back in the octagon.
- Chael Sonnen: Failed three consecutive drug tests, starting with the test conducted after his loss to Anderson Silva. Has since recovered his fighting license, and has moved on to a different promotion.
- Josh Barnett: his spectacular championship win over Randy Couture was overshadowed by a positive result for doping before, during, and after the bout. After recovering from his suspension, moving on to other promotions overseas, and eventually returning to the UFC, a positive result for doping during an out-of-contest test in 2016 eventually led him to request being released from the UFC out of his growing distrust of the US Anti-Doping Agency.
- Nick Diaz: tested positive for marijuana use in 2007 during and after his match with Gomi Takanori. Another positive doping result five years later led to a high-profile court case and another suspension. He remains in hiatus even long after being cleared to return to the ring.
- Wanderlei Silva: Failing to submit to drug tests in 2014 led the Nevada Athletic Commission to ban Silva from fighting for life in the state. The ruling was overturned, however, and was replaced by a three-year limited ban. He has since moved on to a different promotion and continues to fight.