The IAAF World Championships for track and field begin this weekend in Moscow without two of the sport's highest-profile athletes.
Sprinters Tyson Gay and Asafa Powell are out because they tested positive for performance enhancing drugs recently.
More than two dozen other athletes will also miss the meet because of doping.
The BBC's Alex Capstick reports.
- Alex Capstick, sports reporter for the BBC. He tweets @Cappo61.
This segment aired on August 9, 2013.