Taxonomic knowledge may be distinguished into several forms: horizontal, representing links between items at the same level of a taxonomic hierarchy (e.g., dog-cow), and vertical, representing links between items at different hierarchical levels (e.g., dog-animal). Horizontal relations include 3 category types: slot-filler (based on constrained function, i.e., shared function within an event), conventional subcategory (based on constrained, but not event-based, function and/or on arbitrary cultural groupings), and conventional superordinate (based on unconstrained function). 3 experiments–category production, word association, and forced-picture-choice–explored taxonomic and thematic/ schematic knowledge in 4- and 7-year-old children and adults. Results showed preschooler taxonomic knowledge to be restricted to slot-filler categories. Conventional horizontal relations and vertical taxonomic knowledge emerged with age. Slot-fillers played a role in these developments of taxonomic knowledge. Also developing was' task/context sensitive responding, with 7-, but not 4-year-olds, relying on distinct forms of knowledge across tasks.