||The goal of the present study was to assess the relative effectiveness of massed and spaced distribution of practice for learning category members as a function of the level of discriminability (i.e., how similar or different categories are from one another). Ample research has examined the benefits of spaced practice (compared to massed practice) on semantic learning, yet much remains to be understood about how distribution of practice affects abstract category learning. Researchers have suggested that the level of discriminability may determine which presentation type is more beneficial to category learning (Kornell & Bjork, 2008; Kurtz & Hovland, 1956); thus, the present study investigated the effects of distribution of learning (massed v. spaced) and level of discriminability (3 irrelevant characteristics v. 5 irrelevant characteristics) on category learning. Seventy-two participants were randomly assigned to one of four conditions experimental conditions (N = 18 per cell). Participants were presented with examples of three different categories of fictitious superheroes. During the study phase, each example of a superhero was paired with its respective category name. Participants were then tested and asked to identify examples of superheroes (without name pairing). Results of the present study did not find significant differences between distribution of practice on category learning or distribution of practice as a function of level of discriminability on category learning. Although the present study's hypotheses were not supported, these null results have important implications for future research. Implications and future directions for examining abstract category learning are discussed.