Gabriela Szabo won her first major 1,500 metres title on Tuesday then kept the world waiting while she slept on a decision whether to compete in the 5,000 heats in two days' time.
The twice world 5,000 champion and Sydney gold medallist outsprinted fellow-Romanian Violeta Szekely to win the 1,500 in four minutes 00.57 seconds.
She then said she would wait until the morning before deciding whether she would run on Thursday.
Szabo has threatened to boycott the 5,000 metres in protest at the International Association of Athletics Federations (IAAF) decision to allow Russian Olga Yegorova to compete despite a positive drugs test.
Yegorova failed a test for the blood-boosting drug EPO (erythropoietin) but has been allowed to compete because the test did not conform to International Olympic Committee specifications.
Later Derartu Tulu led an Ethiopian clean sweep in the women's 10,000 metres while Amy Mbacke Thiam won Senegal's first world medal of any kind in the women's 400,
Tulu, Olympic champion in 1992 and again last year in Sydney, led an Ethiopian trio who tracked Paula Radcliffe as the Briton made another brave but ultimately doomed victory bid.
In one smooth movement, Tulu, Berhane Adere and 1999 champion Gete Wami flowed past Radcliffe to cross the line in that order after a desperate struggle between the leading pair.
Thiam won in a photo-finish with Jamaican veteran Lorraine Fenton, creating immense excitement in the VIP box seating compatriot and IAAF president Lamine Diack.
Czech Tomas Dvorak won his third successive world decathlon title after taking first place from overnight leader Dean Macey of Briton in the high hurdles, the opening event of the second day.
Dvorak set a championship record of 8,902 points ahead of Estonia's Olympic gold medallist Erki Nool with Macey in third place.
Italian Fiona May repeated her 1995 victory in the women's long jump to atone for her disappointment in Seville two years ago.
May led going in to the final round in Spain but lost the gold to Cuban-born Spaniard Niurka Montalvo.
Swiss Andre Bucher, pushed off the track in Sydney, made no mistake this time in winning the men's 800 metres gold and in the day's other final Cuban Yipsi Moreno claimed her first major title with a win in the women's hammer.