Bounded and unbounded events differ in whether they include an inherent endpoint (Bach, 1986). Even though this distinction can be important for the way events are identified and processed, the literature on event cognition has not focused on such abstract aspects of event structure. In the present study, we asked whether viewers are sensitive to the distinction between bounded and unbounded events in a category learning task. Our results show that people were more successful in forming the category of bounded events than that of unbounded events. We discuss implications of this finding for event cognition.