After holding at 3-3, Smashnova never had more than two points on her serve as Williams took advantage of her looping, heavy topspin groundstrokes.
"She just played a different-pace game, so I pressed a little too much and was hitting the balls a bit long," Williams said. "I needed to add some spin because she's the kind of player where you don't want to get caught up playing her game. That's when things can really get kind of strange. So I kept with my game, playing aggressive, and worked through the errors."
Tenth-seeded Alicia Molik closed a 6-3, 6-2 win over Tatiana Panova with an ace, advancing to face Williams.
"Bring it on!" Molik told the crowd at Rod Laver Arena after reaching the fourth round, matching her best run at a major.
Serena and Venus Williams have made fashion statements on court with their dress designs. At the Australian Open, Spaniards Rafael Nadal and Feliciano Lopez of Spain are doing their best on the men's side, wearing three-quarter-length pants.
Andy Roddick is certain he won't joint that trend.
Roddick was asked Saturday after his straight-sets win over Jurgen Melzer whether the new male fashion statement was a ``little too metrosexual.''
"You said it, I didn't," said Roddick, laughing. "I can't think of anything funny to say that would not get me in trouble. I'm going to leave that one alone."
ACCORDING TO FORM
All top eight women's seeds have advanced to the fourth round at the Australian Open, putting them on track to break a 24-year-old record. The last time all eight reached the quarterfinals here was in 1981.
This time, in seeded order, they are Lindsay Davenport, Amelie Mauresmo, Anastasia Myskina, Maria Sharapova, Svetlana Kuznetsova, Elena Dementieva, Serena Williams and Venus Williams.
In 1981, in the same order, it was Chris Evert, Tracy Austin, Martina Navratilova, Andrea Jaeger, Hana Mandlikova, Pam Shriver, Wendy Turnbull and Evonne Goolagong Cawley.
Four Russians, three Americans and France's Mauresmo make up the international mix now.
The makeup in 1981 was five Americans, including former Czech Navratilova, who became an American citizen in July of that year.
The Australian Open, in its 100th year, set an all-time day attendance record Saturday when 44,517 spectators went to Melbourne Park. That broke the previous record of 42,915 set on the second day of the Open in 2002.