Weir was 30m clear as he came onto the home straight in the 400m
Britain's David Weir made a confident start to his quest to win five Paralympic gold medals, winning heats of the 400m and 5,000m.
And Chris Martin took a silver medal in the discus on the opening day in the Bird's Nest, despite a Paralympic record throw of 28.37 metres.
China's Zhang Lixin set a Paralympic record in another heat of the 400m but Weir is confident for the final.
"I've had a cold so I've been trying to take it easy," he told BBC Sport.
Of the 5,000m he said: "I knew it was going to be fast because the top four were in there and it was quite tough but it felt comfortable."
Brian Alldis failed to finish in his 5,000m heat after the rubber came off his right glove on the third lap.
"I just lost my grip so I couldn't carry on," said Alldis.
"I'm gutted but I'll be back. I suppose it was worth coming out here to witness the atmosphere, its really amazing."
Usually in qualifying the times are slower but I ran the same time I ran in the final four years ago
South Africa's Oscar Pistorius made short work of his 100m semi-final, winning in 11.16 seconds, although the event is considered the weakest of the three he competes in.
"Usually in qualifying the times are slower but I ran the same time I ran in the final four years ago," he said.
"On Tuesday night [in the final] I should be aiming sub-11."
Scot Libby Clegg, 18, made it to her 100m final, lowering her personal best for the second time in the day, clocking 12.69, to win her heat as the fourth fastest qualifier.
"I was quite relaxed on the start line, maybe too much, but I'm quite nervous now thinking about the final," she said.
Fellow Brit Tracey Hinton paid for a poor start and did not qualify for the T11 100m final.
In the discus, Martin had to settle for silver because of factoring system based on the level of disability, giving gold to Latvian Aigars Apinis.
"I'm really pleased with silver but I so much wanted gold," said Martin, 36, from Mansfield, who was fourthin Athens four years ago before apparently retiring.
"I'm disappointed with the way the event unfolded because I'd already had my six throws when he made the winning throw.
"I'll try and drag my body through another four years for London."
Martin added that he felt sorry for his teammate Dan West who finished a disappointed sixth after taking silver four years ago, saying: "He'll be back in his second event."
In the morning session, Hollie Arnold - at 14 the youngest member of the GB athletics squad - produced her longest throw of the year in the javelin but her 29.10m was only enough to take 11th place.
"I'm really disappointed," she said. "I wanted to get over my personal best of 32.25m and was actually aiming at 36 but my shoulder was hurting me."
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Video - Martin scores a silver