There where further performances of Tosca in Milano (La Scala) with Tebaldi in April 1954, followed by a surprisingly well performed Eugenenio Oneghin in May, also with Tebaldi and Ettore Bastianini. Tosca was repeated in Chicago in November with Steber and Gobbi, after a successful Lucia with Callas. Von Karajan wanted him for his Carmen at La Scala in January 1955, then a crucial performance came in May 1955 at La Scala. Luchino Visconti was producing La Traviata - Carlo Mario Giulini was the conductor - and Visconti had picked Callas as Violeta, whom he worshipped and found ideal as the tragic protagonist. The media coverage and fuzz around Callas was simply too much for di Stefano, who abandoned the production after the premiere performance in protest.

He met Callas in Milano later that season for a recording of Rigoletto (EMI) under Tullio Serafin, with Gobbi in the title role, and recorded La Traviata with Antonietta Stella and Gobbi (also EMI) practically at the same time. Shortly after he travelled with La Scala and Callas to Berlin for Lucia di Lammermoor under von Karajan, where ha had some troubles and was replaced by Giuseppe Zampieri in the final scene. He appeared, however, in splendid voice in Chicago in October for I Puritani with Callas (cond. Rescigno), La Boheme with Tebaldi in November (cond. Serafin) and yet again Callas for Madama Butterfly the same month (cond. Rescigno). Then he made his first performance in 3 years at the Met. The opera was Carmen, opposite Risë Stevens, November 1955, followed by Faust with Dorothy Kirsten and Jerome Hines in December, then Rigoletto with Roberta Stevens and Robert Merrill and Tosca with Zinka Milanov and Tito Gobbi (cond. Mitropoulos) in January 1956.

1956 brought about a change of repertorty for di Stefano. He started leaning towards spinto roles, first anticipated with Carmen in Milano and New York (1955), then heavier roles such as Cavalleria Rusticana, in which he appeared in February 1956 and La forza del destino in March, both at the Teatro Massimo in Palermo under the baton of Serafin, Pagliacci in Milano under Sanzogno in April, La Gioconda in August at the Arena di Verona, conducted by Votto, Il Trovatore in Milano with Callas, under von Karajan, August/September, Aida with Stella under Votto in December and finally Mascagni's Iris, also in December 1956, conducted by Gavazzeni and starring Boris Christoff. In between these taxing performances he had celebrated one of his greatest successes, having been invited by von Karajan to Wien and the Staatsoper for Lucia in June. He co-starred with Callas, Panerai and Zaccaria.

Giuseppe di Stefano had become the world's leading lyric tenor within short, but was not prone to secure his position. The breach with the Met in 1952 was just one such example, the feud with Visconti at La Scala in 1955 another. A change of repertory towards the spinto range might be considered a third. His voice was not suited for heavier roles and certainly not the manner in which he employed it. He sang with an open and uncovered note, "voce aperta," as Lauri-Volpi coined it, and with an abuse of "note spalancate," he was risking a premature dissolution. The first symptoms were becoming apparent in the late 50's, anticipated by asthmatic problems that were to make the rest of his career a struggle.