Finnish brothers Joonas Lindgren and Niklas Lindgren started their 470 campaign in fine fashion with a bullet and a second place finish to lead the overall leaderboard.
A stunning start in race one by Ridgely Balladares and Chavez Rommel (PHI) was overcome by the Finnish sailors, who took and extended their lead to win 34 seconds ahead of runners-up, Gideon Kliger and Eran Sela (ISR).
Philip Sparks and David Kohler (GBR) took an early lead in race two for the Yellow Fleet but the race was won by Mathew Belcher and Malcolm Page with the Lindgren brothers settling for second.
In the Blue Fleet, New Zealand's Paul Snow-Hansen and Jason Saunders maintained a strong lead throughout race one, with a real battle for the other top spots. Swedish pair Anton Dahlberg and Sebastian Ostling, Panagiotis Mantis and Pavlos Kagialis (GRE) and France's Pierre Leboucher and Vincent Garos battled throughout the race before finishing second, third and fourth respectively.
The last race of the day for Men's 470 Blue Fleet was won by Luke Patience and Stuart Bithell (GBR). Gabrio Zandona and Pietro Zucchetti (ITA) improved on their previous eighth place to finish second, followed by Sime Fantella and Igor Marenic (CRO).
The Men's 470 sailors resume proceedings at 12:30 local time tomorrow.
Despite light winds delaying the start of the Women's RS:X competition, the breeze blew in unexpected results for the yellow fleet with World No. 1 Blanca Manchon (ESP) finishing 46th overall with lower than expected finishes in both her races.
Manchon's compatriot Marina Alabau (ESP) fared better, with a third and an 11th place finish putting her in sixth place for the day.
The Chinese Women's RS:X team thrived in the afternoon's light winds, with all four of the country's athletes placing in the top 10 in the Yellow Fleet.
In the Blue Fleet, wins for Lee Korzits (ISR) and Laura Linares (ITA), and solid results in their other race, had the two sailors high in the progressive results.
But Bryony Shaw (GBR) recorded a second and a third to share the overall lead with Korzits.
The Women's RS:X event is scheduled to continue on Tuesday on Centre Course at 12:30 local time.
Five-time Finn world champion Ben Ainslie took an early lead on the first day of his event at the Perth 2011 ISAF Sailing World Championships, winning both his races with ease in the Yellow Fleet.
Ainslie won from the front in the first race but had to come from fifth place to take another win over compatriot and current world champion Ed Wright to put himself firmly at the top of the fleet.
"I didn't have a particularly good start (in the second race) but I was good on the downwind reach and was in front at the second mark," he said.
On why he was so good at downwind sailing, he said, "It has to do with the conditions and technique. After all I have been sailing a lot. You just get into a groove and go with it."
In the Blue Fleet, the 2004 Olympic silver medalist Rafa Trujillo (ESP) led the first race from start to finish while Pieter-Jan Postma (NED) put a poor race behind him to lead all the way and take the second race. Trujillo rounded off a great day with a third place, to end the day in second overall behind Ainslie. A second and a fifth for the 2008 silver medalist Zach Railey (USA) leaves him in third overall.
The Finn event is scheduled to continue on Tuesday at 13:00 local time on the Leighton course.
Women's Match Racing
Silke Hahlbrock (GER) put an end to Anna Tunnicliffe's undefeated run in the final flight of Women's Match Racing on Monday, with the German managing to come from behind to get over the line in front as the World #1 lagged with sea weed caught on her keel.
In the previous flight, Hahlbrock (GER) had managed to edge out Australia's Nicky Souter, also previously undefeated, in another tight match.
It was also a great day for Finland's Silija Lehtinen, who is yet to lose a match, despite stiff competition throughout the day. At the conclusion of day three, Finland remained the only undefeated team.
Women's Match Racing is scheduled to contine on Tuesday at 10:00 on the Inner Harbour course.
Belgium's Evi van Acker dominated racing in the Yellow Laser Radial Fleet, with the world number two winning both her races.
Meanwhile World #5 Paige Railey (USA) had a mixed day finishing her first race in eighth, before claiming a second place in race two.
In the Blue Fleet, Veronika Fenclova (CZE) and Marit Bouwmeester (NED) were the stand out performers.
Fenclova, the world number three, finished first and third while current World #1 Marit Bouwmeester (NED) was consistent with a second and a third.
The Laser Radial competition is scheduled to continue on the Parmelia Course at 12:00 local time.
The Perth 2011 ISAF Sailing World Championships website will bring you results, tracking, live updates and all the latest news both on and off the water.