Xiang Liu of China led all qualifiers as the men's 60 metre hurdles competition got underway. The 20-year-old indoor and outdoor bronze medallist won the first heat in 7.63, with Cuban Yoel Hernandez (7.64) close behind.
Defending champion Allen Johnson of the United States advanced easily after finishing third behind Stanislavs Olijars (7.64) and Jamaican Dwight Thomas (7.65) in heat three. Swede Robert Kronberg (7.69) advanced as well.
"I feel fine," said Johnson, smiling. "It's good to get things going."
Jamaican outdoor record holder Maurice Wignall won the fourth heat in 7.67, with Shaun Bownes of South Africa (7.73) and Briton Mohammed Sillah-Freckleton (7.75) also advancing easily.
In heat two, American Duane Ross stumbled over the second hurdle after clipping the first, and was carried from SportArena on a stretcher. Cuba's Yuniel Hernandez won the heat in 7.59, with Charles Allen of Canada a distant second in 7.69.
Masato Naito, Japan's national record holder outdoors, added the indoor record to his collection with a 7.77 run in heat two, but did not advance.
The top three from each heat plus the four next fastest move on to this afternoon's semi-finals.