ɪn nˈaɪntiːnhˈʌndɹɪd fˈɪfti, mæzˈɛɾi wˈʌn ðə ɡɹˈændz pɹˈiː ʌv bˈɛldʒəm ænd ðə nˈɛðɜːləndz ænd dᵻfˈiːɾᵻd dʒˈɛf dˈuːk fɚðə fˈaɪvhˈʌndɹɪd sˌiːsˈiː wˈɜːld tʃˈæmpiənʃˌɪp.
In 1950, Masetti won the Grands Prix of Belgium and the Netherlands and defeated Geoff Duke for the 500cc World Championship.