This essay deals with a conspicuous feature of early modern experimental reports: references to multiple repetitions. I examine an episode from the history of research on venomous snakes, the dispute between Francesco Redi and Moyse Charas about the cause of death from viper bites. I identify different kinds of repetitions that are described and specify the various different roles that are attributed to repetitions in experimental reports. I argue that repetition (the successive reproduction of one's own experimental trials) should be distinguished from replication (reproducing other investigators' experiments). At first, replications played hardly any role in the exchange, but references to repetitions were crucial to show that contingencies had been obviated, to support inductive generalizations, and to specify the exact cause of an experimental effect. Notably, it appears that the replication of effects by different experimental means was not part of the repository of methodological notions that Redi and Charas brought to bear on their experiments. Reruns and repetitions with variations (including complementary trials) bore the epistemic weight.