The beginning of the 1990s marked a golden age for Grand Prix motorcycle racing. The rivalry between Wayne Rainey and Kevin Schwantz was in full flow while Mick Doohan started to come into his own. Eddie Lawson had switched to Cagiva and started to have some respectable results. In a one year quirk, only 13 races counted. Competitors were allowed to drop their two worst scores. The Yugoslavia round was dropped because of the civil war and replaced with a Grand Prix of Europe at Jarama. The Brazilian round was also dropped at the last minute over track safety concerns and replaced with a race held at Le Mans. The inaugural Malaysian Grand Prix was held at Shah Alam.
For the 1991 season, Michelin decided to supply only the Rothmans Honda team with tires; everybody else used Dunlops.
Luca Cadalora won the 250 title in a dominating fashion with eight wins. In the 125 class, Italian teenager Loris Capirossi swept to the title for the second consecutive year.