Previous research suggests that infants can calculate simple arithmetic (Wynn, 1992). This study sought to replicate this finding and examine how familiarization may influence response. Experiment 1 confirmed that 3- to 5-month-old infants looked longer at an incorrect outcome (1 + 1 = 1) when no familiarization trials were presented. Experiment 2 presented infants with 8 familiarization trials (either to the possible or impossible mathematical event). When familiarized to the incorrect outcome, infants looked longer at the correct outcome; however, when familiarized to the correct outcome, infants showed no preference for either display. Experiment 3 confirmed that infants could have become familiarized to both 1 and 2 dolls during the familiarization to the possible event and raised the possibility that infants may not process the display as a mathematical event, but rather as a series of unconnected stimuli. (Contains 5 figures and 1 table.)