The robust effects of knowledge on memory for domain-relevant information reported in previous research have largely been attributed to improved organizational processing. The present research proposes the distinctiveness theory of skilled memory, which states that knowledge improves memory not only through improved organizational processing but also through more effective processing of differences between items in the context of the similarity defined by organization. Individuals with either high or low knowledge about NFL football were presented with lists containing items from the target domain (NFL football) or a control domain (cooking). Individuals either performed a category sorting task, a pleasantness rating task, or both. Results on a surprise free recall test later showed knowledge effects on memory (high knowledge individuals had greater recall than low knowledge individuals for football items but not for cooking items). Secondary measures established that the knowledge effect on memory was due not only to better organizational processing but also to more effective item-specific processing.