Irish hurdler Derval O'Rourke safely progressed from her opening qualifier at the World Championships but Paul Hession exited from the men's 200m in disappointing fashion.
O'Rourke ran a safe heat to finish a comfortable second in 13.07 - .54secs behind fastest qualifier and gold medal contender Australia's Sally Pearson.
However, Hession could only manage 21.02 to take fourth in his heat.
Hession was well outside his season's best of 20.51.
Being drawn in lane two may not have helped Hession but he was actually pipped for the third automatic qualifying place by lane-one runner Finland's Jonathan Astrand who clocked 20.87.
The heat was won by Norway's Jaysuma Saidy Ndure in 20.65 ahead of American Darvis Patton (20.80).
Hession's qualifier proved one of the slower of the seven heats and he was well outside the final fastest loser's time of 20.70.
Last year's European Championship silver medallist O'Rourke appeared to adopt a cautious approach in her heat as Pearson stormed to victory.
The Irish athlete was .16secs ahead of third placer Colombia's Brigitte Merlano and will be expecting to run a lot faster in Saturday morning's semi-final (1115 BST).
O'Rourke, fourth in Berlin two years ago, will almost certainly have to run close to her national record of 12.65, set in last year's European Championships.
The Cork athlete, whose season's best is 12.84, will have American gold medal contender Danielle Carruthers and British hopeful Tiffany Porter for company in the semi-final with only the first two guaranteed a place in the final.
The Irish women's 4x400m squad improved their national record by over two seconds with a 3:27.48 clocking and finished 12th overall.
The performance by Marian Heffernan, Joanne Cuddihy, Claire Bergin and Michelle Carey will boost the Irish team's hopes of qualifying for next year's Olympics.
Only 16 nations will compete in the 4x400m event in London.