In the early 1960s Mahler’s music became a vital stimulus for Henze’s compositional technique and aesthetics. Particularly important were its exploration of formal crises, the incorporation of ‘old’ musical materials, and its apparently direct expression of love and beauty. These aspects confirmed Henze’s desire to break out of the restrictions of Darmstadt dogma, into an apparently anachronistic expressive and technical freedom. This article explores structural and hermeneutic relationships between two of Henze’s works of the period – Being Beauteous and The Bassarids– and Mahler’s Fifth Symphony. In Being Beateous the expressive aspects of cadences in the Adagietto of Mahler’s Fifth Symphony are shown to be crucial models for Henze’s exploration of Rimbaud’s poetic expression of the destruction and revitalization of beautiful form. In The Bassarids an intertextual allusion to the second movement of Mahler’s Fifth Symphony is taken as a signal of Mahlerian ‘breakthrough’ as Pentheus has a vision of Dionysian revelries. Henze’s fragmented, broken, allusive, and eclectic musical textures are interpreted as characteristic expressions of eroticism, as well as being more generally symptomatic of his understanding of Mahler’s importance for twentieth-century music.