But he exploded out of the blocks in Rome to hit the front early on and power away from compatriot Asafa Powell, who was second in 9.91 secs.
Britons Greg Rutherford and Robbie Grabarz won the long and high jumps.
Steve CramBBC athletics commentator
Bolt gets pulled around all over the place. He went to the Champions League final in the week before Ostrava, so it was a case of having a few days to get himself sorted out. He came to the stadium looking like he meant business, and we got a serious performance. He is carrying an awful lot on his shoulders going into the Olympics; it is not just about winning for him. The whole of this sport looks for him to deliver something special.
The performance of Grabarz was particularly noteworthy, as he cleared 2.33m to set a new personal best and the leading height in the world this year, while Rutherford continued his recent good form by winning the long jump with a leap of 8.32m, 3cm short of his new joint British record.
But the undoubted star of the night was Bolt, who admitted some relief at returning to the sort of style and times for which he is known.
"I knew I could do it," the triple Olympic champion told BBC Sport. "Since I've been in Europe I've not been sleeping regularly, so after Ostrava I made sure I started going to bed earlier and eating right.
"I felt extememly well today, so it's come back and I am pleased.
"People expect me to do well all the time but I expect a lot of myself also, so it is not a pressure for me. I came out tonight not to prove anything to the world but to tell myself I've still got it, and I'm working my way from here."
Powell was left complaining he was unable to hear the starter's gun properly, while Frenchman Christophe Lemaitre trailed in a distant third in 10.04.
World record eludes Koech
The other outstanding display of the night saw Kenyan
run the third fastest time ever in the 3,000m steeplechase, powering home in 7:54:33, seven-tenths of a second outside the mark set by Saif Saaeed Shaheen in Brussels eight years ago.
There was a surprise in the women's 100m as
of the Ivory Coast set a new personal best and national record of 11 seconds dead to pip Jamaican duo Shelley-Ann Fraser-Pryce and Kerron Stewart.
Britain's Nathan Woodward finished fifth, while former world champion Felix Sanchez fell after coming off the final hurdle feeling cramp in his calf, but later declared the problem was not serious.
lost his lottery funding at the end of a poor season in 2011, but that forced him to re-dedicate himself to the sport and it paid dividends as he cleared each height from 2.20m at the first attempt until failing to clear 2.35m.
Analysis - BBC's Mark Butler
We can move Robbie Grabarz up the list of British athletes with the potential to take an Olympic medal in London. Not only did he defeat a field including the reigning world champions indoors and out, he also produced the highest jump in the world this year outdoors. This was the best win by a British high jumper since Dalton Grant won the European Indoor title in 1994.
"I achieved what I set out to achieve," the 24-year-old said. "I have been jumping very well in training but been trying to keep a lid on it. That's why I started my season so late."
also progressed smoothly with jumps of 8.04, 8.07 and 8.11m before responding to Russian Aleksandr Menkov (8.17) and South African Godfrey Mokoena (8.13) overtaking him by pulling out a superb 8.32 to win comfortably. Chris Tomlinson, who shares the British record of 8.35, could only manage fourth with 7.77.
With Chambers running the first leg, Britain finished second behind Canada, but the
British men's 4x400m quartet
won their race comfortably, Jack Green bringing them home on the final leg ahead of Botswana.
Ahoure stuns favourites in 100m
finished strongly to take third in the men's 800m behind 17-year-old Kenyan winner Leonard Kosencha, while
finished third in the women's javelin with a season's best throw of 64.73m, with Barbora Spotakova of the Czech Republic taking victory with 68.65m.
"I knew I only had one or two throws in me because I was ill with food poisoning during the week," Sayers said. "But I beat the world champion and Olympic bronze medallist so I am pretty happy with my day's work."
pulled out of her 400m hurdles race with a hamstring strain, while world indoor champion
suffered a shoulder injury in the triple jump.
Aldama, 39, landed awkwardly in the pit after jumping 14.65m in the second round - her longest outdoors for six years - and passed the rest of her four jumps. She will have a scan on the injury in London on Friday.
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