Publications
Partners
In another Roland Garros mismatch involving the in-form top seed, the 31-year-old American was in control from the start on the Suzanne Lenglen showcourt, winning the first set in just 23 minutes.
Cirstea was facing an embarrassing whitewash, but she rallied briefly at the start of the second set and even had two break points to lead 3-2.
But she failed to take either of these and Williams simply stepped on the accelerator again to race away and end the remaining pockets of resistance from the Romanian.
The win was the 27th in a row for Williams - the best unbeaten run of her career - and it took her into a fourth round match against the winner of the tie between Roberta Vinci of Italy and Petra Cetkovska of the Czech Republic.
She has dropped just six games in three matches as she campaigns for the 16th Grand Slam title of her career, but just the second in Paris where she last won in 2002.
Williams reached the semi-finals at Roland Garros the following year and since then has fallen four times at the quarter-final stage, but last year she was upset in the first round by Frenchwoman Virginie Razzano.
French Open results on Friday (x denotes seeded player):
Men:
Third round:
David Ferrer (ESP x4) bt Feliciano Lopez (ESP) 6-1, 7-5, 6-4
Roger Federer (SUI x2) bt Julien Benneteau (FRA x30) 6-3, 6-4, 7-5
Second round:
Rafael Nadal (ESP x3) bt Martin Klizan (SVK) 4-6, 6-3, 6-3, 6-3
Tommy Haas (GER x12) bt Jack Sock (USA) 7-6 (7/3), 6-2, 7-5
Mikhail Youzhny (RUS x29) bt Federico Del Bonis (ARG) 6-3, 6-7 (5/7), 7-5, 6-4
Jerzy Janowicz (POL x21) bt Robin Haase (NED) 6-4, 4-6, 6-4, 6-3
Nikolay Davydenko (RUS) bt Denis Istomin (UZB) 6-4, 7-5, 6-2
Richard Gasquet (FRA x7) bt Michal Przysiezny (POL) 6-3, 6-3, 6-0
John Isner (USA x19) bt Ryan Harrison (USA) 5-7, 6-7 (7/9), 6-3, 6-1, 8-6
Stanislas Wawrinka (SUI x9) bt Horacio Zeballos (ARG) 6-2, 7-6 (7/2), 6-4
Janko Tipsarevic (SRB x8) bt Fernando Verdasco (ESP) 7-6 (7/3), 6-1, 3-6, 5-7, 8-6
Women:
Third round:
Serena Williams (USA x1) bt Sorana Cirstea (ROM x26) 6-0, 6-2
Second round:
Maria Kirilenko (RUS x12) bt Ashleigh Barty (AUS) 6-3, 6-1
Marion Bartoli (FRA x13) bt Mariana Duque (COL) 7-6 (7/5), 7-5
Maria Sharapova (RUS x2) bt Eugnie Bouchard (CAN) 6-2, 6-4
