After a succession of good results as an amateur, Gramigni made his Grand Prix debut in 1990 riding an Aprilia in the 125cc Class, ending the season in ninth position. He won his first race at the 1991 Czechoslovakian Grand Prix and finished the season ranked seventh in the championship with 90 points.
In 1992, he edged out Italian Fausto Gresini to win the 125cc world championship, with wins in Malaysia and Hungary. Gramigni moved up to the 250cc class in next season, first with the Gilera team before switching back to Aprilia. It was a disappointing season, as he scored only 2 points. He competed two more seasons in the 250 class, 1994 with the Aprilia, and in 1995 with Honda. After a two year sabbatical, he entered one race in the 500cc class at the 1997 Malaysian Grand Prix before ending his Grand Prix career.