South Korea's Park Tae-Hwan won the 100m and 400m freestyles at the Santa Clara Grand Prix swimming meeting, taking his gold tally to three in two days.
Park, who opened the meeting on Thursday with a victory in the 800m freestyle, surged to the lead in the final 25 meters to win the 100m free in 48.85sec.
Former Olympic 50m free gold medallist Anthony Ervin, attempting a comeback after 12 years, touched second at 49.95 with Aaron Wayne third at 50.04.
Park won the 400m free in 3:44.96 with Ryan Napoleon of Australia second in 3:49.79. Canada's Ryan Cochrane was third in 3:50.56.
Dana Vollmer was a two-time winner, capturing the 100m freestyle and 100m butterfly -- both ahead of fellow American Natalie Coughlin.
Vollmer won the 100 free in 54.38 seconds, with Coughlin second in 54.77 and Australian Brittany Elmslie third in 54.89.
Vollmer returned to win the 100m fly in a meet record of 57.03sec, with Coughlin second in 58.44.
Japan's Kosuke Kitajima, the two-time defending Olympic champion who will be going for a three-peat in London, won the men's 200 breaststroke in 2:13.24.
Kitajima already owns the top time of 2012 at 2:08.00 from Japan's Olympic Trials in April.
Scott Weltz took second in 2:14.27, while Mexico's Christian Schurr Voigt was third (2:14.35).
Takuro Fujii led a Japanese one-two in the men's 100m fly in 52.79. Takeshi Matsuda was second in 52.84.
Bronte Barratt of Australia dominated the women's 400m free with a time of 4:06.13, just off her fastest time this year of 4:05.74.
Chelsea Chenault was second in 4:08.95, while Australia's Kylie Palmer was third in 4:09.79.
