The musical Merrily We Roll Along (1981), Sondheim’s sixth consecutive collaboration with director Hal Prince, was revised extensively during a month of poorly received preview performances but still closed after just two weeks of mixed reviews and poor sales. Believing in the show’s promise, over the next eleven years Sondheim and co-author George Furth rewrote it repeatedly, making Merrily possibly the most revised work in Sondheim’s Broadway canon. Correspondence and successive drafts of the script in collections at the New York Public Library document this process and include intriguing ideas such as several possible endings for what is now the first scene, a fraught party. The article will discuss these documents as well as Sondheim’s published version of the lyrics with commentary in 2010, and two differing stagings in 2012 of the prologue and party scene. Another central area of exploration concerns how directors of revivals such as James Lapine (in 1985 and 2012), Paul Kerryson (in 1992), Michael Grandage (in 2000) and Maria Friedman (in 2012) helped reshape the staging, and, to a limited extent, the words and music. The complexities of this collaborative revision process challenge Sondheim’s assertion in 2010 that the script was finalized by 1992.