A FIM véglegesítette a 2004-es esztendőben rajthoz álló csapatok és pilóták névsorát.
125 cc
| 3 | Hector Barbera | SPA | Aprilia | Seedorf Racing |
| 6 | Mirko Giansanti | ITA | Aprilia | Matteoni Racing |
| 7 | Stefano Perugini | ITA | Gilera | Gilera Racing Team |
| 8 | Manuel Manna | ITA | Malaguti | Semprucci Malaguti |
| 10 | Julian Simon | SPA | Honda | Angaia Racing |
| 11 | Mattia Angeloni | ITA | Honda | Angaia Racing |
| 12 | Thomas Lüthi | SUI | Honda | Elit Grand Prix |
| 14 | Talmácsi Gábor | HUN | Malaguti | Semprucci Malaguti |
| 15 | Roberto Locatelli | ITA | Aprilia | LCR |
| 16 | Raymond Schouten | NED | Honda | Arie Molenaar Racing |
| 19 | Alvaro Bautista | SPA | Aprilia | Seedorf Racing |
| 21 | Steve Jenkner | GER | Aprilia | WWC |
| 22 | Pablo Nieto | SPA | Aprilia | Master � MXonda - Aspar Team |
| 23 | Gino Borsoi | ITA | Aprilia | Racing World |
| 24 | Simone Corsi | ITA | Honda | Team Scot |
| 25 | Tóth Imre | HUN | Aprilia | Team Hungary |
| 26 | Dario Giuseppetti | GER | Honda | Elit Grand Prix |
| 27 | Casey Stoner | AUS | KTM | Red Bull KTM |
| 28 | Jordi Carchano | SPA | Aprilia | Matteoni Racing |
| 32 | Fabrizio Lai | ITA | Gilera | Gilera Racing Team |
| 33 | Sergio Gadea | SPA | Aprilia | Master � Mxonda � Aspar Team |
| 34 | Andrea Dovizioso | ITA | Honda | Team Scot |
| 36 | Mika Kallio | FIN | KTM | Red Bull KTM |
| 41 | Youichi Ui | JPN | Aprilia | Abruzzo Racing Team |
| 42 | Gioele Pellino | ITA | Aprilia | Abruzzo Racing Team |
| 44 | Joshua Waters | AUS | Honda | Ajo Motorsport |
| 47 | Angel Rodriguez | SPA | Derbi | Derbi Racing Team |
| 48 | Jorge Lorenzo | SPA | Derbi | Derbi Racing Team |
| 50 | Andrea Ballerini | ITA | Aprilia | Fontana |
| 52 | Lukas Pesek | CZE | Honda | Ajo Motorsport |
| 54 | Mattia Pasini | ITA | Aprilia | LCR |
| 58 | Marco Simoncelli | ITA | Aprilia | WWC |
| 63 | Mike di Meglio | FRA | Aprilia | Racing World |
| 66 | Vesa Kallio | FIN | Aprilia | Team Hungary |
250 cc
| 2 | Roberto Rolfo | ITA | Honda | Fortuna Honda |
| 6 | Alex Debon | SPA | Honda | Troll Honda BQR |
| 7 | Randy de Puniet | FRA | Aprilia | LCR |
| 8 | Naoki Matsudo | JPN | Yamaha | Yamaha Kurz |
| 9 | Hugo Marchand | FRA | Aprilia | Zoppini Abruzzo |
| 10 | Alfonso Nieto | SPA | Aprilia | Repsol � Aspar Team |
| 11 | Joan Olive | SPA | Aprilia | Campetella Racing |
| 12 | Arnaud Vincent | FRA | Aprilia | Equipe de France � Scrab GP |
| 14 | Anthony West | AUS | Aprilia | Team Zoppini Abruzzo |
| 15 | Christian Gemmel | GER | Honda | Kiefer Castrol - Honda Racing |
| 16 | Johan Stigefelt | SWE | Aprilia | Aprilia Germany |
| 19 | Sebastian Porto | ARG | Aprilia | Repsol � Aspar Team |
| 21 | Franco Battaini | ITA | Aprilia | Campetella Racing |
| 24 | Toni Elias | SPA | Honda | Fortuna Honda |
| 25 | Alex Baldolini | ITA | Aprilia | Matteoni Racing |
| 26 | Daniel Pedrosa | SPA | Honda | Telefonica Movistar Honda 250cc |
| 28 | Dirk Heidolf | GER | Aprilia | Aspar Junior Team |
| 33 | Hector Faubel | SPA | Aprilia | Aspar Junior Team |
| 34 | Eric Bataille | FRA | Honda | Troll Honda BQR |
| 36 | Erwan Nigon | FRA | Yamaha | Yamaha Kurz |
| 40 | Max Sabbatani | ITA | Yamaha | NC World Trade |
| 44 | Taru Sekiguchi | JPN | Yamaha | NC World Trade |
| 50 | Sylvain Guintoli | FRA | Aprilia | Campetella Racing |
| 51 | Alex de Angelis | RSM | Aprilia | Aprilia Racing |
| 54 | Manuel Poggiali | RSM | Aprilia | Aprilia Racing |
| 57 | Chaz Davies | GBR | Aprilia | Aprilia Germany |
| 73 | Hiroshi Aoyama | JPN | Honda | Telefonica Movistar Honda 250cc |
| 77 | Grégory Lefort | FRA | Aprilia | Equipe de France � Scrab GP |
| 96 | Jakub Smrz | CZE | Honda | Arie Molenaar Racing |
MotoGP
| 3 | Max Biaggi | ITA | Honda | Camel Honda Team |
| 4 | Alexandre Barros | BRA | Honda | Repsol Honda |
| 6 | Makoto Tamada | JPN | Honda | Camel Honda Team |
| 7 | Carlos Checa | SPA | Yamaha | Gauloises Fortuna Yamaha |
| 9 | Nobuatsu Aoki | JPN | Proton KR | Proton Team KR |
| 10 | Kenny Roberts | USA | Suzuki | Team Suzuki MotoGP |
| 11 | Ruben Xaus | SPA | Ducati | D�Antin MotoGP |
| 12 | Troy Bayliss | AUS | Ducati | Ducati Marlboro Team |
| 15 | Sete Gibernau | SPA | Honda | Telefonica Movistar Honda MotoGP |
| 17 | Norifumi Abe | JPN | Yamaha | Fortuna Gauloises Tech 3 |
| 21 | John Hopkins | USA | Suzuki | Team Suzuki MotoGP |
| 33 | Marco Melandri | ITA | Yamaha | Fortuna Gauloises Tech 3 |
| 45 | Colin Edwards | USA | Honda | Telefonica Movistar Honda MotoGP |
| 46 | Valentino Rossi | ITA | Yamaha | Gauloises Fortuna Yamaha |
| 50 | Neil Hodgson | GBR | Ducati | D�Antin MotoGP |
| 56 | Shinya Nakano | JPN | Kawasaki | Kawasaki Racing Team |
| 65 | Loris Capirossi | ITA | Ducati | Ducati Marlboro Team |
| 66 | Alex Hofmann | GER | Kawasaki | Kawasaki Racing Team |
| 67 | Shane Byrne | GBR | Aprilia | Aprilia Racing |
| 69 | Nicky Hayden | USA | Honda | Repsol Honda |
| 80 | Kurtis Roberts | USA | Proton KR | Proton Team KR |
| 99 | Jeremy McWilliams | GBR | Aprilia | Aprilia Racing |
| Harris WCM engedélyezésre vár |