Boulez’s conducting career developed in the United States in the mid 1960s, when he was invited by George Szell to become guest conductor of the Cleveland Orchestra. From then until 1971, he conducted in Cleveland, Boston, Chicago, Los Angeles and New York, and was the principal conductor of the New York Philharmonic Orchestra during 1971–7. In later years, he conducted often with the Chicago Symphony Orchestra (1991–2010). In the context of these engagements, this chapter focuses on Boulez’s involvement with the music of a number of North American composers whose works he conducted, primarily in New York and Chicago. In New York, he pioneered the Prospective Encounters concerts in Greenwich Village, the Rug Concerts and a number of mini-festivals. While Elliott Carter was by far his most favoured North American composer, in Paris he conducted and recorded the work of Frank Zappa and finally in Chicago he conducted several compositions by Augusta Read Thomas.