Mark Lewis-Francis qualified fastest for Saturday's 100m semi-finals on the opening day of the UK Trials and Championships in Birmingham.
Lewis-Francis ran 10.30 seconds with Dwain Chambers, Marlon Devonish, Craig Pickering and Christian Malcolm among the others to qualify for the semis.
In the women's 400m Olympic champion Christine Ohuruogu qualified quickest.
But there was bad news for 400m teenage hurdler Jack Green who pulled out with an illness.
That illness looks certain to cost the European Under-23 champion a place at next month's World Championships in Daegu.
With European and Commonwealth champion Dai Greene running the flat 400m this weekend instead and therefore needing the one discretionary place available, Green will miss out if the first two in the trials have the qualifying standard, with Nathan Woodward and Rhys Williams looking set to do just that in Saturday's final.
"I'm absolutely gutted," Green wrote on Twitter. "I'm just hoping this will not be the end of my season regarding the World Championships but I'll be doing all I can to get healthy."
In the women's 800m, long-time rivals Jenny Meadows and Marilyn Okoro eased into Saturday's semi-finals, while Laura Samuel won the women's triple jump with a jump of 13.67m - well short of the qualifying standard of 14.30m.
Anyika Onuora was the quickest qualifier in the women's 100m running 11.46secs, with Laura Turner and Jeanette Kwakye also safely through to Saturday's semis.
Ohuruogu was the pick of the bunch in the 400m ahead of hurdles specialist Perri Shakes-Drayton, Lee McConnell, Shana Cox, Nicola Sanders and Kelly Sotherton. But her time of 52.08 was well short of the leading times in the world this year.
The 27-year-old has not broken 50 seconds for the 400m since the Olympic final in 2008. And her best time this year of 51.49secs leaves her a lowly 33rd in the world rankings - and only third in Britain.
World champions Jessica Ennis and Phillips Idowu and double European champion Mo Farah are some of the other star names in Birmingham this weekend as they look to cement their place in the Great Britain and Northern Ireland team for the World Championships in South Korea next month.