Miami:World number ones Roger Federer and Justine Henin advanced at the $7.54 million ATP and WTA hardcourt event on Monday, Henin in straight sets and Federer thanks to an injury retirement.
Swiss superstar Federer was leading Robin Soderling 6-4, 3-0 when the Swedish player retired with illness, advancing the world number one into a fourth-round match.
"There is a big difference between not playing at all and playing a set and a half. I prefer today," Federer said. "I get the feel of the tournament playing a match and I'm able to handle the conditions."
Federer, upset by American Mardy Fish at the Indian Wells semi-finals in his most recent prior event, will next face Argentina's Jose Acasuso, who eliminated Israel's Dudi Sela 6-4, 6-4.
Australian Open runner-up Jo-Wilfried Tsonga was eliminated by fellow Frenchman Julien Benneteau 6-3, 6-3 in another third-round match.
Benneteau, ranked 72nd, awaits the winner of a night match between US sixth seed Andy Roddick and Czech qualifier Ivo Minar.
Belgium's Henin, who won titles at Sydney and Belgium in four starts this year, beat Russia's Elena Vesnina 6-2, 6-2 in a fourth-round match.
This is Henin's first event after a Dubai quarter-final loss to Italy's Francesca Schiavone.
Russian third seed Svetlana Kuznetsova, the 2006 winner here and a finalist last week at Indian Wells, defeated Israeli 16th seed Shahar Peer 7-6 (7/4), 6-3, to book a quarter-final date with US sixth seed Venus Williams.
Williams defeated Denmark's Caroline Wozniacki 6-3, 6-3. Also reaching the final eight was Russian Dinara Safina, who ended the run of US tennis mum Lindsay Davenport 6-3, 6-4.
In other matches on the men's side, Russian fourth seed Nikolay Davydenko reached the round of 16 by defeating Italy's Simone Bolelli 6-7 (5/7), 7-5, 6-1 and will next face Croatian wild card Mario Ancic or Argentina's Juan Monaco.