135,000 loyal enthusiasts of motorcycle racing turned up at Assen to watch Round 9 of the 1991 World Championship Series. It was a dramatic day's racing and the 500 event fielded big-name stars including John Kocinski, Wayne Rainey, Eddie Lawson, Kevin Schwantz, Wayne Gardner and Sito Pons. After a speedy but cautious start on a wet grid with Doohan in the lead, rain stopped the race but it was drama all the way at the restart. The 250 cc event was a thriller with a three-way battle between points leader Luca Cadalora, Pier-Francesco Chili and Wilco Zeelenberg.