appeared regularly at the opera houses in Genoa, Naples, Palermo, and at the Verona Arena. Outside Italy, he appeared at many houses throughout Europe and in the United States. In 1955 he made his first appearance at the Teatro Nacional Sao Carlos in Lisbon as Alfio. In 1956 he made his American debut at the San Francisco Opera as Count di Luna in Verdi's Il trovatore. He sang several more roles with that house that season including Amonasro in Verdi's Aida, Gianciotto in Zandonai's Francesca da Rimini, Sharpless in Puccini's Madama Butterfly, and Scarpia in Puccini's Tosca. In 1957 he made his first appearance with the Vienna State Opera as Iago in Verdi's Otello. In 1959 he sang in the world premiere of Luciano Chailly's La riva delle sirti at the Monte Carlo Opera and made his debut at the Lyric Opera of Chicago. In 1960 he made his debut with the Philadelphia Lyric Opera Company as Amonasro with Leontyne Price in the title role. In 1966 he sang Amonasro for the inauguration of Jesse H. Jones Hall for the Performing Arts with the Houston Grand Opera. The Metropolitan Opera years In March 1960 Colzani was approached by Rudolf Bing, General Manager of the Metropolitan Opera in New York City, with an invitation to join the roster at the Met after the sudden death of Leonard Warren during a performance of La forza del destino left a vacancy at the house. He agreed and on April 7, 1960, Colzani made his debut at the Met in the title role of Verdi's Simon Boccanegra with Renata Tebaldi as Amelia, Richard Tucker as Gabriele Adorno, Jerome Hines as Jacopo Fiesco, and Dimitri Mitropoulos conducting. He stayed with the company for sixteen more seasons, portraying such roles as Amonasro, Barnaba in Ponchielli's La Gioconda, Don Carlo in Verdi's La forza del destino, Enrico in Donizetti's Lucia di Lammermoor, Gérard in Giordano's Andrea Chénier, Iago, Jack Rance in Puccini's La fanciulla del west, Scarpia, Tonio in Leoncavallo's Pagliacci, and the title roles in Falstaff, Macbeth, Nabucco, and Rigoletto among others. Colzani's most frequent role at the Met was Scarpia; portraying the role more than forty times. Opera News stated that, "Undoubtedly Colzani's highest-profile assignment at the Met was Falstaff in the first performances of Franco Zeffirelli's much-loved 1964 production of Verdi's opera, conducted at its premiere by Leonard Bernstein." His final and 272nd performance