When children learn categories, they do not learn isolated facts but rather systems of knowledge. These systems of knowledge are composed of property-property (e.g., things with wings tend to have feathers), property-role (e.g., things with eyes tend to eat), and role-role (e.g., things that eat tend to sleep) correlations. Research has shown that even young children have knowledge of property-property and property-role correlations, but there has been little direct evidence of their knowledge of role-role correlations or for how children might acquire this knowledge. We found that 5-year-olds have knowledge of role-role correlations and 2- and 3-year-olds have different degrees of knowledge of property-role correlations. Two-year-olds needed multiple properties to infer an appropriate role, whereas 3-year-olds needed only a single property (e.g., eyes or wheels). These results suggest that role knowledge may first be linked to object (or literal) similarity, then to clusters of properties, to a single property, and finally to other roles. (Contains 5 figures and 1 table.)