In the 1950s and 1960s, many composers, influenced by Arnold Schoenberg and Anton Webern, embraced serial compositional techniques. Tonal music became atonal and composers, such as Pierre Boulez from France and the German composer, Karlheinz Stockhausen, championed this new compositional approach. This chapter defines serialism and how composers applied it to works for percussion instruments. Music examples include Stockhausen’s solo work, Zyklus, with its totally original notational system, and a setting of an E. E. Cummings poem, Circles, by the Italian composer Luciano Berio. American composer Charles Wuorinen’s use of Milton Babbitt’s “time point” system in both his solo work Janissary Music and his forty-five-minute Percussion Symphony is presented, as is the work of Argentine composer Alberto Ginastera, who contributed to the literature one of the twentieth century’s largest percussion works, Cantata para América Mágica, for dramatic soprano and fifty-three percussion instruments. A discussion of percussion solo and ensemble works by the Greek composer, architect, and mathematician Iannis Xenakis completes the chapter.