Jamaican Usain Bolt won the 100m title at the world athletics championships in Beijing, crossing the line in 9.79 seconds to reassert his status as the fastest man on the planet.
American Justin Gatlin, the form sprinter of the last two years, finished second in 9.80 to take silver, while Andre de Grasse of Canada and American Trayvon Bromell crossed the line together in third place in a time of 9.92.
1. Usain Bolt (Jamaica) 9.79
2. Justin Gatlin (U.S.) 9.80
3. Andre De Grasse (Canada) 9.92
3. Trayvon Bromell (U.S.) 9.92
5. Mike Rodgers (U.S.) 9.94
6. Tyson Gay (U.S.) 10.00
7. Asafa Powell (Jamaica) 10.00
8. Jimmy Vicaut (France) 10.00
9. Su Bingtian (China) 10.06
Bolt, the reigning Olympic champion has now not been beaten in the 100m or 200m in six major global championships going back to 2007, although he was disqualified from the shorter race at the Deagu world championships in 2011.
The 29-year-old will go for successive world championship sprint sweeps in Beijing, the site of his breakthrough triumph at the 2008 Olympics, with the 200 metres final scheduled for Thursday.
Meanwhile, Olympic champion Jessica Ennis-Hill, who only decided to compete four weeks ago, regained the heptathlon world title after what she described as her "hardest year ever".
Ennis-Hill became a mother for the first time 13 months ago, and had originally intended for 2015 to be a "transition" year to prepare for the defence of the Olympic title in Rio de Janeiro.
The Briton's victory followed a dramatic twist in the day's first discipline, the long jump, when her closest rival, teammate Katarina Johnson-Thompson, scored zero points following three foul jumps.
Ennis-Hill jumped 6.43 metres and threw the javelin 42.51 metres to give her an 86-point lead before the final event, the 800 metres.
Ennis-Hill, who won the world title in Berlin in 2009, finished with 6,669 points.