The first medals of the day were decided in the women’s marathon, where 33-year-old Kiplagat, who led a Kenyan sweep in 2011, started steadily, then patiently tracked surprise front-runner Valeria Straneo until the 40km mark.
She then broke clear to triumph in 2:25:44, leaving the 37-year-old Italian to take silver ahead of Japan’s Kayoko Fukushi.
Straneo, who had her spleen and gall bladder removed three years ago, was delighted with her silver and performed a cartwheel on the track after crossing the line.
There was drama in the decathlon where double defending world champion Trey Hardee crashed out after no-heighting in the high jump.
Hardee, who triumphed in Berlin and Daegu, and took Olympic silver last year, strained a hamstring and failed to clear 1.90m.
Olympic champion Ashton Eaton’s 47.02 seconds in the 400m was the fastest in 30 years of world championship decathlons and earned him a slender lead over 20-year-old Gunnar Nixon.
Britney Reese, Olympic long jump champion and winner of the last two world titles, cut it fine in qualifying as she scraped into the final in 12th and last place on countback with 6.57m, way down on her best of 7.25m set earlier this year.