(CNN) -- Venus and Serena Williams are both through to the second round of the Bank of the West Classic in Stanford, California, their first tournament since contesting the Wimbledon final earlier this month.
Venus Williams cruised through her opening match in the Bank of the West Classic.
Top seed and Wimbledon champion Serena was made to work hard by China's Li Na before progressing 6-3 7-6.
Second seed Venus had a more comfortable passage through, cruising past Canadian Stephanie Dubois 6-2 6-3.
"It was a great match to get my rhythm, hit a lot of balls and work on my shots," Venus, who won here in 2000 and 2002, told reporters. "It's all about the mentality. I usually adjust pretty quickly. I do want to try new and different things."
The older Williams sister has a superb record in the tournament, reaching the final in six of her seven appearances in the Stanford University hard-court event.
Meanwhile, defending champion Aleksandra Wozniak has gone out, losing 6-4 4-6 7-5 to Daniela Hantuchova of Slovakia in a marathon match that lasted two hours and 33 minutes.
Wozniak became the first Canadian in 20 years to capture a Tour title when she won the 2008 tournament.