Defending champion Freddie Spencer was the pre-season favorite to win the championship however, teething problems with Honda's new V4 and early season injuries squelched his hopes to repeat. In spite of his problems, Spencer still took five wins. Eddie Lawson lived up to his nickname of Steady Eddie with four wins and four second places to secure his first 500cc world championship on a Yamaha. Randy Mamola also had three wins to finish second on a factory backed Honda.
Yamaha also claimed the 250 crown with Frenchman Christian Sarron taking the honors ahead of a strong challenge from Real-Rotax mounted Manfred Herweh. Angel Nieto would win a thirteenth world championship with six wins in a row before sitting out the final two races. Stefan Dörflinger would be the first ever 80cc champion after the class displacement was increased from 50cc.