Bojana Jovanovski and Naomi Broady made winning starts at the Carlsbad Classic on Monday.
Serbian Jovanovski, the third seed, overcame wildcard Alexandra Stevenson 7-6 (7-3) 3-6 6-1 in the first round of the hard-court event.
There were nine breaks of serve, but Jovanovski came out on top against the 34-year-old American.
It was a relatively good day for the seeds at the WTA 125k Series tournament in Carlsbad, California.
Broady was too good for Jovanovski's countrywoman Jovana Jaksic, claiming a 6-3 7-5 victory.
The British fourth seed served 12 aces and was not broken.
Fifth seed Nicole Gibbs progressed when Alla Kudryavtseva retired with the American leading 6-3 3-2.
The only seed to fall was Rebecca Peterson, who went down to Macedonia-born Swiss Amra Sadikovic 6-4 7-5.
Jennifer Brady was a 7-5 6-1 winner over Danielle Lao, Samantha Crawford breezed past Grace Min 6-2 6-3 and teenager Katerina Stewart beat Paula Cristina Goncalves 7-5 6-3.