After practicing as a lawyer for five years while training his voice under I. Jossifov in Sofia, he trained under Mme. Safirowa in Russia and Johannes Kemter in Dresden.
As early as 1954, he was singing the heroic title role in the Georgian opera Keto und Kote by W.I. Dolidse in the Municipal Theater of Turnovo. From 1962-65 he was heard with the ensemble of the Russian Opera House in Bulgaria. Then he became known in East Germany, where he enjoyed great success. He sang at the Döbeln Theater from 1965-68, from 1968-71 at the Municipal Theater of Magdeburg, from 1971-75 in Halle/Saale abd was called in 1975 as the principal Heldentenor at the Berlin State Opera, where he was heard until 1984. During a 1975 guest engagement at the Dresden State Opera, he scored a particular success as Tristan. He sang the role at the Bayreuth Festival in 1976 and in 1982-83, while adding Tannhäuser.
Having begun his career singing the most demanding dramatic parts in the Italian repertoire, in later years he became known as a great Wagner interpreter, appearing as a guest throughout the world. In 1982 he triumphed as Tannhäuser at the Vienna State Opera where he took over the title role for the suddenly-indisposed Reiner Goldberg. In 1981, he answered a call to the Metropolitan Opera, where he debuted as Tristan. From 1984, he appeared principally at the German Opera House, Berlin, at the State Opera Houses of Vienna and Munich and at the Cologne Opera. In 1987, he appeared at the Bern Municipal Theater and at the Wiener Staatsoper as Tannhäuser. In 1990, he was a guest artist in Cologne; in 1991 he appeared in Vienna as Tristan and in 1991 at Covent Garden as the Götterdämmerung Siegfried. His older brother, Wenko Wenkoff (1921-92) was also a well-known tenor.
Recordings: Eterna, Ars Vivendi, Balkanton, Philips (Tannhäuser, also on video).
Wagner: Siegfried Dass der mein Vater nicht
Wagner: Tannhäuser Inbrunst im Herzen