In working with Stephen Sondheim as lyricist on West Side Story, Bernstein seemed to have forged an important new collaboration with an edgy young writer to contrast with his previous musicals with musical comedy writers Comden and Green. Yet the young Sondheim saw himself as a composer-lyricist, perhaps even with more of an emphasis on the music than the words, so the success of the team was short-lived. This chapter examines primary source accounts of their work together, considering how they met, what they thought of each other, and how productive their creative tensions were. The chapter also briefly addresses their other short-lived projects, including the abandoned The Exception and the Rule.