Previous research has demonstrated dissociations between categorization and recognition performance in amnesic patients, supporting the idea that separate memory systems govern these tasks. However, previous research has also demonstrated that these dissociations are predicted by a single-system model that allows for reasonable parameter differences across groups. Generally, previous studies have employed categorization tasks that are less demanding than the recognition tasks. In this study, we distinguish between single-system and multiple-system accounts by testing memory-impaired individuals in a more demanding categorization task. These patients, just like previous amnesic participants, show a dissociation between categorization and recognition when tested in previously employed paradigms. However, they display a categorization deficit when tested in the more challenging categorization task. The results are interpreted as support for a single-system framework in which categorization and recognition depend on one representational system.