Heather Watson marked her first week as British number one with victory over Eleni Daniilidou in round one of the Mercury Insurance Open in Carlsbad.
The 20-year-old, who won the Bank of the West Classic doubles title on Sunday, beat 112nd-ranked Daniilidou of Greece 6-3 6-3 at the California event.
Watson next meets seventh seed Yanina Wickmayer or qualifier Chan Yung-Jan.
But British number two Anne Keothavong is out after she succumbed 6-4 6-0 to Marina Erakovic of New Zealand.
Keothavong also lost in the doubles, going down 6-2 1-6 10-8 against Kai-Chen Chang and Noppawan Lertcheewakarn.
But Watson progressed as she and Slovak team-mate Janette Husarova overcame fourth seeds Natalie Grandin and Vladimira Uhlirova 6-4 7-5.
At the Swedish Open in Bastad, Laura Robson lost 6-4 7-6 (7-4) to third seed Anabel Medina Garrigues in the opening round.
Robson reached her maiden WTA semi-final at last week's Italiacom Open and plays doubles with Watson at the Olympics.
Keothavong and Elena Baltacha will represent Team GB in the singles