He had his best year in 1955 when he won the 350cc French Grand Prix and finished the season in seventh place in the 350cc world championship.
[2] Duilio Agostini was born to a well off family that owned the hotel restaurant Al Porto, now known as the Giardinetto, at Mandello del Lario on the shores of Lake Como; Guests included many important personalities linked to motorcycling, such as Omobono Tenni, Stanley Woods, Terzo Bandini, Primo Moretti and Ugo Prini.
Duilio worked for Moto Guzzi first in the customer service department, and finally, in 1947, as the official test rider alongside of Engineer Giulio Cesare Carcano.
His best year was 1955 when he won the French motorcycle Grand Prix and ended the season in seventh place in the 350cc World Championship.
In 1993 he retired from the dealership leaving it totally in the hands of his daughter Alis who already managed it from 1981, initially with her sister Lindy.