DescriptionMany studies have found that infants in the first year of life use continuous amount, rather than discrete number, to represent small sets of objects. Using a looking-time paradigm, we show that twelve-month-olds use discrete quantity representations even when continuous quantity information is available, while nine-month-olds are just beginning to attend to discrete quantity. In the first study, twelve-month-old infants were required to track the changing locations of objects and sets of objects on a trial-by-trial basis. Infants were surprised to see both one and three objects when two were expected, despite the total surface area of the sets remaining constant. A second study found that twelve-month-old infants tracked the locations of a singleton and a pair and were surprised when the sets unexpectedly swapped positions. In a third study using the same methodology as the first, nine-month-old infants detected changes from two to three objects, but fail to detect changes from two to one. A fourth study investigated whether twelve-month-old objects can track sets adding up to more than three objects. Twelve-month-olds infants used shape information to individuate across pairs and track a total of four objects. Infants who were familiarized to two distinct pairs (for a total of four objects) looked longer at an outcome of only two objects, while infants who were familiarized to two mixed pairs (for what appeared to be a total of two objects) did not look longer. Finally, twelve-month-old infants were tested on their ability to represent sets of two and three, for a total of five objects. Pilot data suggest that infants can do so. These studies suggest that by twelve months of age, infants can reason about discrete quantity in addition to tracking continuous quantity. We propose that even young infants may have access to mechanisms of innate number, and represent at least small numbers using integer concepts.