Debutants
Clark Sheehan is the youngest debutant in World Championships in 1990. There are 48 debutants.
| # | Rider | Team | Age |
|---|---|---|---|
| 1 | SHEEHAN Clark | United States | 21y + 148d |
| 2 | STURGESS Colin | Great Britain | 21y + 261d |
| 3 | JALABERT Laurent | France | 21y + 276d |
| 4 | KRIEGER Dominik | Germany | 22y + 69d |
| 5 | HALUPCZOK Joachim | Poland | 22y + 91d |
| 6 | BOUWMANS Eddy | Netherlands | 22y + 215d |
| 7 | LELLI Massimiliano | Italy | 22y + 274d |
| 8 | ASADA Akira | Japan | 22y + 278d |
| 9 | DE KONING Louis | Netherlands | 22y + 318d |
| 10 | LODGE Harry | Great Britain | 22y + 344d |
| 11 | HOLDEN Rob | Great Britain | 23y + 2d |
| 12 | MARTÍNEZ Miguel Ángel | Spain | 23y + 66d |
| 13 | DE VRIES Gerrit | Netherlands | 23y + 112d |
| 14 | BOWEN Bart | United States | 23y + 133d |
| 15 | LEBLANC Luc | France | 24y + 29d |
| 16 | FARMER David | United States | 24y + 183d |
| 17 | VAN DEN ABEELE Frank | Belgium | 24y + 242d |
| 18 | HASHIZUME Kazuya | Japan | 24y + 270d |
| 19 | STOCKTON Kurt | United States | 24y + 320d |
| 20 | WELTZ Kenneth | Denmark | 24y + 346d |
| 21 | URBONAS James | United States | 25y + 56d |
| 22 | KABASAWA Koki | Japan | 25y + 183d |
| 23 | AMPLER Uwe | East Germany | 26y + 22d |
| 24 | LOUVIOT Philippe | France | 26y + 172d |
| 25 | LEANIZBARRUTIA Alberto | Spain | 27y + 154d |
| 26 | CARTER Michael | United States | 27y + 183d |
| 27 | YASUHARA Masahiro | Japan | 27y + 210d |
| 28 | VOLPI Alberto | Italy | 27y + 267d |
| 29 | CENGHIALTA Bruno | Italy | 27y + 271d |
| 30 | RAAB Uwe | East Germany | 28y + 38d |
| 31 | JASKUŁA Zenon | Poland | 28y + 90d |
| 32 | KUMMER Mario | East Germany | 28y + 119d |
| 33 | GIOVANNETTI Marco | Italy | 28y + 151d |
| 34 | ADAMS Kenny | United States | 28y + 220d |
| 35 | MARKI Hansrüdi | Switzerland | 30y + 76d |
| 36 | IVANOV Ivan | Soviet-Union | 30y + 116d |
| 37 | MULDER Gary | United States | 30y + 198d |
| 38 | BARTH Thomas | East Germany | 30y + 202d |
| 39 | GIRAMONDO Agostino | Australia | 30y + 302d |
| 40 | ACHERMANN Alfred | Switzerland | 31y + 47d |
| 41 | JENTZSCH Olaf | East Germany | 31y + 273d |
| 42 | WAGHMARE Mukesh | India | |
| 43 | KIM Kyu Geun | South Korea | |
| 44 | DOIPHODE Ravindra | India | |
| 45 | JUNG Heang Mo | South Korea | |
| 46 | ATAGI Hirofumi | Japan | |
| 47 | ADSULE Jeetendra | India | |
| 48 | NOGUSHI Yoshihiro | Japan |