In 1964, he wrote "The Effect of Gamma Rays on Man-in-the-Moon Marigolds", his first and most successful play. The play ran off-Broadway in 1970, and on Broadway in 1971, and he received the 1971 Pulitzer Prize for Drama for the work. However, this play also received criticism for being too elliptical or too difficult to understand. Still, it was also made into a 1972 movie by 20th Century Fox, directed by Paul Newman and starring his wife Joanne Woodward. Soon thereafter, Charlotte Zolotow, a vice-president at Harper & Row, contacted him about writing for her book label.