All the favourites advanced safely in the both 400m hurdles events, with a wide-open men's race headed by American Michael Tinsley and Puerto Rica's Javier Culson likely to be one of the highlights of Thursday night's programme.
American former world champion Bershawn Jackson qualified for the semis but left the track with a heavily-iced hamstring shaking his head.
There was also disappointment for Jamaican former world junior champion Kaliese Spencer, who won her heat but was disqualified for taking her trail leg around, rather than over, one of the hurdles.
Olympic decathlon champion and world record holder Ashton Eaton had won a high-class competition on Sunday but, in contrast, the heptathlon looked desperately short of star quality in the absence of Olympic champion Jessica Ennis-Hill, Russian world champion Tatyana Chernova and Olympic silver medallist Lilli Schwarzkopf of Germany.
Hoping to take full advantage and complete a memorable family double is Brianne Theisen Eaton, the Canadian who married the decathlon winner last month.
She started impressively on Monday with a 13.17 100m hurdles for a hefty 1099 points and recorded a 1.83m high jump; while Katarina Johnson-Thompson ran a 13.49 before jumping 1.83m.
However, she had to settle for second place going into the shot put behind Ukraine's Ganna Melnichenko.
Melnichenko, second-fastest in the hurdles, at last managed to raise some noisy support from the specially flown-in block of several hundred Ukraine fans clad in yellow and blue t-shirts, as she cleared a personal best 1.86 to lead on 2135 points.
Germany's Robert Harting got his bid for a third successive title off to an impressive start when he launched the discus 66.62 metres with his first throw to march into Tuesday's final.
Pole Piotr Malachowski, who has been operating in Harting's shadow for the past four years and was memorably denied the world title by the German's personal-best last throw in 2009, also progressed safely with a 66.00m opener.
Harting's younger brother Christoph, however, missed out.
After Bolt won a men's 100 metres final containing an unprecedented four Jamaicans on Sunday, Olympic champion Shelly-Ann Fraser-Price leads the island's bid for the double in the women's event later on Monday.
Jamaica and the United States each have four women through to the semis, with Nigeria's Blessing Okagbare, who won a long jump silver on Sunday, hoping to crash the final party.
Five other titles will also be decided later on Monday, with the United States hoping for a first global clean sweep for more than half a century in the 110m hurdles.