Jamaica’s seven-time Olympic champion Usain Bolt ran 20.28 seconds to reach the semi-finals of the men’s 200m.
Bolt, who won the 100m title on Sunday, jogged home in the final 50 metres to win the ninth of 10 heats.
Britain’s Adam Gemili, Danny Talbot and Nethaneel Mitchell-Blake qualified, as did Justin Gatlin of the United States.
“I hate the mornings so I am happy to have this out the way. It’s a good start and I’m happy,” 29-year-old Bolt told BBC Sport.
Gemili ran 20.20 in finishing second in his heat while Gatlin, the 100m silver medallist, clocked 20.42 to win heat five.
Talbot equalled his personal best in running 20.27 in heat one and Mitchell-Blake clocked 20.24 in the final heat.
The semi-finals take place at 02:00 BST on Thursday.
Elsewhere in Tuesday’s morning session, American Christian Taylor retained the men’s triple jump title, while Croatia’s Sandra Perkovic took gold in the women’s discus.
McColgan & Bradshaw qualify for finals
Eilish McColgan qualified for the women’s 5,000m final but fellow Britons Steph Twell and Laura Whittle missed out.
McColgan finished fifth in her heat in 15 minutes 18.20 seconds in a race won by Ethiopia’s 10,000m champion Almaz Ayana, who clocked 15:04.36.
Twell’s 15:25.90 was not enough to earn qualification as a fastest loser, while Whittle ran 15:31.30 in heat one.
“I’m over the moon, I wanted it so badly. “There is no pressure on me now, I couldn’t be happier,” McColgan said.
British pole vaulter Holly Bradshaw, who finished sixth at London 2012, qualified automatically for Saturday’s final, clearing 4.60m.
“I’m 24 and in my second Olympic final. I am so excited and I can’t wait,” she told BBC Sport.
Charlie Grice is through to the men’s 1500m semi-finals following an appeal. The Briton had been pushed by Norway’s European champion Filip Ingebrigtsen in the closing stages of their heat.
Grice faltered badly when he was bumped, crossing the line 11th in 3:48.51 seconds, but was reinstated after a protest by the British team and Ingebrigtsen was disqualified.
Team-mate Chris O’Hare qualified automatically after finishing fourth in his heat in 3:39.26.
In the women’s 100m hurdles, American-born Briton Cindy Ofili won her heat in 12.75 seconds to reach Wednesday’s semi-finals.
Ofili’s sister, Tiffany Porter, also progressed, running 12.86 to finish second behind Germany’s Cindy Roleder.
American Brianna Rollins, the 2013 world champion, was the fastest qualifier in 12.54.
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