Controversial American sprinter Justin Gatlin underlined his status as 100m gold medal favourite as he produced the fastest time in the first round.
Gatlin, who has twice served doping suspensions, clocked 9.83 seconds in the sixth heat, albeit with the assistance of a 2.1m/s tailwind.
Reigning world and Olympic champion Usain Bolt won the seventh heat in 9.96 into the slightest headwind and grinned afterwards despite a slow start.
Bolt, beset by a pelvic injury for much of the season, has produced only two sub-10 second 100m performances all summer and looked to be working hard for the first 60 metres as he continues to search for the magic of old.
While Gatlin has been consistently running 9.8secs this summer, and arrived in Beijing on a 27-race unbeaten run stretching back two years, Bolt will go into Sunday’s semi-finals and final hoping to hit a peak at exactly the right time.
Gatlin oozed the same confidence and easy form he has shown throughout the year, once again seemingly unaffected by the furore around his appearance here after those two drugs bans.
Also impressive was his young compatriot Trayvon Bromell, whose 9.91secs saw him win the fourth heat, while France’s Jimmy Vicault and Jamaica’s Asafa Powell also went under 9.96.
Tyson Gay, world champion in Osaka eight years ago, cruised through the second heat in 10.11secs, but while British champion CJ Ujah came through as an automatic qualifier with a smooth 10.05 behind Bromell, there was disappointment for James Dasaolu.
Dasaolu has a personal best of 9.91 but got his heat totally wrong, shutting off too early before being swamped by his rivals.
The third Briton, Richard Kilty, made it through as a fastest loser and was again fortunate after easing off too early to drop down to fourth in the third heat in 10.12.