Antonioni’s Blow-Up is one of the most significant and controversial films of the 1960s. Its success brought increased international recognition not only to its director but to Julio Cortázar, the author of the story that inspired the film. Because of the extreme complexity and ambiguity of both Blow-Up and its source, “Las babas del diablo,” critics have been unable to agree in their interpretations of either work, and they agree even less on the extent of Cortázar’s influence on Antonioni. A close analysis of the two works, with careful focus on the relationship between the creators and their protagonists and on the tension between the narratives and their self-conscious forms, reveals that many of the difficulties in interpretation are due to a priori assumptions of readers and viewers alike and that the similarities between the film and the story are far greater than has been supposed.