Radwanska's defence starts well
World number four Agnieszka Radwanska opened her Sony Open title defence with a comfortable straight sets win over Hsieh Su-wei.
Poland's Radwanska took a 6-3 6-2 victory over her Taiwanese opponent at Crandon Park as she bids to defend the title she won last by beating Maria Sharapova in the final.
Radwanska, a winner in Auckland and Sydney this year, broke her opponent four times in a match which lasted 65 minutes.
"I am very happy to have a quick match," Radwanska told the tournament website.
"The first match is always a little bit tough and tricky, especially coming from Indian Wells, where we have a little bit different conditions."
China's fifth seed Li Na made a successful return from a seven-week injury absence with a 6-3 6-1 victory over Kiki Bertens.
Li, who injured her left ankle in the Australian Open final, won in 67 minutes against the Dutch player.
Li said: "I wasn't nervous today before the match, but I was excited.
"For the last six or seven weeks I haven't played any tournaments so I was happy with the result today and to win my first match after such a long time."
There was an upset win for wild card Ajla Tomljanovic of Croatia as she beat Germany's 24th seed Julia Goerges 7-6 (7/4) 6-2.
Belgium's Kirsten Flipkens was a 6-4 6-2 winner over Swiss qualifier Stefanie Voegele.
In the men's draw, Taipei's Lu Yen-hsun beat American Robby Ginepri 7-5 6-1 and there were also wins for Belgium's Olivier Rochus, Uzbekistan's Denis Itsomin, France's Guillaume Rufin, Australia's Bernard Tomic and Colombian duo Alejandro Falla and Santiago Giraldo.