They face a formidable task around the 4.727km / 2.937 miles Montmelo circuit, preventing World Champion and Championship-leader Valentino Rossi securing his fourth consecutive victory of the season. Riding the RCV five-cylinder 990cc four-stroke Honda, Rossi has been in brilliant form, which was clearly illustrated by his much-celebrated victory in front of the home fans at Mugello in Italy two weeks ago. His only defeat of the season came in South Africa and that by his team-mate Tohru Ukawa, who lies second in the championship, 43 points adrift of Rossi. Both tested very successfully at the Montmelo circuit pre-season, which was not the case for Yamaha who found the going tough. However, the team have made significant progress since then, especially with the introduction of the new chassis in Italy. This vital race on Sunday will show if their progress is enough to halt the Honda charge, where speeds in excess of 200mph are expected on the long start and finish straight.

It will be tough for the rest of the pack to outwit this flying quartet, although Loris Capirossi put in a superb lap in the pre-season test riding the NSR 500cc Honda Pons bike. The Italian still lies a battling third in the championship and finished third in the race last year behind Rossi and Biaggi. However, Capirossi and Norick Abe, riding the Yamaha d'Antin machine are separated by just three points in their battle for third in front of the four-strokes of Biaggi and Checa. Brazilian Alex Barros, Capirossi's team-mate, celebrates his 200th Grand Prix on Sunday and he shares sixth place with Checa in the championship after finishing fifth in Mugello.

Daijiro Kato won the 250cc race last year, but after a good start to his MotoGP career has crashed his NSR Honda at the last two meetings. The Japanese rider will be looking to score points to improve his eighth place in the title chase. The injury jinx continues to plague the Red Bull Yamaha team with Frenchman Jean Michel Bayle, who replaced the injured Garry McCoy in France and Italy, ruled out on Sunday with torn muscles in his left arm. He will be replaced by 22-year-old German Alex Hofmann who joins American John Hopkins; the 19 year-old Californian who has impressed by scoring points at every round of his debut season.

The Proton KR team of Nobuatsu Aoki and Jeremy McWilliams will be looking for a change of fortune after both seizing in Mugello while former 250cc World Champion, Frenchman Olivier Jacque seems to have got over his jump start problems on the Yamaha Tech 3 bike. Suzuki continue the accelerated development of their GSV-R four-stroke by bringing in Japanese Superbike Champion Akira Ryo to join Kenny Roberts and Sete Gibernau in the next three races. Ryo produced a brilliant debut for the machine by finishing second in the opening Grand Prix at a rain lashed Suzuka in Japan. Frenchman Regis Laconi has given the RS Cube Aprilia a superb start to its development by scoring points in every round this year, including an eighth place in Mugello two weeks ago.

Spaniard Fonsi Nieto comes into the 23-lap 250cc race with a 15-point championship lead, and is also hoping to cure slow starting problems with his Aprilia. Nieto has problems with the handling of his Aprilia when it has a full tank of fuel and has produced some memorable rides through the field in the later stages of races. Italian Marco Melandri bounced back into championship contention with his second victory of the season in Mugello also on an Aprilia, to move into second place in front of the consistent Roberto Rolfo, riding the Honda Gresini machine. Italian Franco Battaini's chances of his first Grand Prix victory have been spoilt by late race collisions, while former 125cc star Toni Elias, Nieto's team-mate, will threaten with support from the home crowd after finishing fourth in Mugello.

As always the 125cc championship is producing some breathtaking races and the 22-lap encounter on Sunday should be no exception. World Champion Manuel Poggiali won a truly memorable battle in Mugello to lead the championship by a single point on his Gilera from the Aprilia of Frenchman Arnaud Vincent. Italian veteran Lucio Cecchinello won the race last year and holds third place in the championship by just one point from 16-year-old Spaniard Daniel Pedrosa. Watch out also for Youichi Ui who was second in Mugello on the Spanish Derbi machine.