Defending champion Valentino Rossi won his second premier class title by winning 11 races and scoring 355 points.
[10][11] Valentino Rossi, riding the four-stroke Honda RC211V bike, won the first race of the season at Suzuka under wet conditions.
Suzuki's test rider Akira Ryō, who raced as a wildcard entry, and Yamaha's Carlos Checa completed the all four-stroke podium.
Max Biaggi handed the four-stroke Yamaha YZR-M1 its first win in the Czech Republic Grand Prix at Brno, while Rossi had to retire due to tyre problems.
[1] In the Pacific Grand Prix, Honda Pons rider Alex Barros won his first race riding the RC211V bike.
[16] In the following race at Sepang, Yamaha expanded their four-stroke presence by providing the YZR-M1 bikes to Tech 3 pair Olivier Jacque and Shinya Nakano.
The season started with a wet race at Suzuka which was won by Japanese wildcard rider Osamu Miyazaki, who was riding for Daytona Yamaha team.
[25] Melandri continued his streak to six consecutive wins and extended his lead in the standings to 37 points after the Czech Republic Grand Prix.
[27][28] Aprilia's winning streak was broken when Yamaha's Sebastián Porto won the Rio de Janeiro Grand Prix under wet race condition.
[30] With 52 points lead and three races to go, Melandri only need to finish in front of Nieto in the Malaysian Grand Prix to clinch the championship.
The 125cc entry list was headlined by defending champion Manuel Poggiali and two-time championship runners-up Youichi Ui and Noboru Ueda.
There were five other riders who have previously won a 125cc race: Masao Azuma, Lucio Cecchinello, Stefano Perugini, Simone Sanna and Arnaud Vincent.
Arnaud Vincent, who returned to Aprilia after a year with Honda, won the opening race at Suzuka under wet condition.
[39] Poggiali won the following race at Catalunya with a late overtake at the finish line over Spanish teenager Daniel Pedrosa.
[41] Vincent, who led the championship in the first four races, returned to the top of the podium with two consecutive wins at Donington Park and Sachsenring.
[42][43] After finishing third behind Cecchinello and Pedrosa at Brno, Vincent won the wet Portuguese Grand Prix and retook the championship lead from Poggiali.
[48] However, Poggiali won the following race at Phillip Island while Vincent finished in fourth to reduce the lead back to eight points.
The Rookie of the Year title was won by Finnish rider Mika Kallio who scored 78 points with the Red Devil Honda team.
[51] The following sixteen Grands Prix were scheduled to take place:[52][53] The following changes are made to the regulation for the 2002 season:[54][55] FIM released a 20-rider entry list on 13 March 2002.