The favourites to win the 100m title at the World Championships in Beijing, Justin Gatlin and Usain Bolt, both eased into the semi-finals after coming through their respective heats unscathed.
Gatlin was met with a chorus of boos from the crowd, but set the fastest time of the session, 9.83s, while Olympic champion Bolt also won his heat, posting 9.96s to finish just ahead of Gatlin's American compatriot Mike Rodgers (9.97s).
Other notable names that impressed during Saturday's heats are young American Trayvon Bromell (9.91s) and Frenchman Jimmy Vicaut (9.92s).
The battle between Gatlin and Bolt is one of the most eagerly anticipated head-to-heads in the 100m in recent times, partly because of their contrasting reputations.
Bolt is the squeaky clean poster boy of sprinting who holds the world record and is a two-time Olympic champion. Gatlin on the other hand has twice been suspended from the sport on doping offenses and is often met with boos when he competes, despite being unbeaten in his last 27 races.
Former world champion Tyson Gay also won his heat but finished well down on the standings after posting 10.11sec, while Qatar’s Femi Ogunode (9.99s) and Andre De Grasse of Canada (9.99s) were the others to break the 10-second barrier.
The semi-finals take place on Sunday.