Analogical comparison of 2 provided cases promotes spontaneous analogical transfer by encouraging a more abstract representation of a target principle. This is widely understood as a process of schema abstraction that aids retrieval from memory in the absence of superficial similarity. The category status hypothesis states that if knowledge about a target principle is represented as a relational category, it is easier to activate as a result of categorizing (as opposed to cue-based reminding). To investigate these 2 pathways to spontaneous transfer (schema retrieval vs. categorization), participants were assigned to different study conditions: (a) standard comparison of 2 analogs; (b) standard comparison followed by a second comparison of 2 new analogs; or (c) a guided Category-building task based on a foundation of sequential summarization with additional categorization supports. Experiment 1 showed improved spontaneous transfer in the Category-building task relative to Single-comparison--the gold standard for encouraging spontaneous transfer. Experiment 2 demonstrated that the Category-building task led to more frequent spontaneous structure-based retrieval than either comparison-based task. This suggests that the transfer improvements observed in Experiment 1 are attributable to the Category-building task making superficially dissimilar prior knowledge more accessible. Experiments 3a and 3b tested alternative explanations of this finding and provided evidence that the effectiveness of the Category-building task arises from encouraging the construal of a target principle as a relational category. These findings support categorization as a critical factor in explaining successful spontaneous analogical retrieval and toward instructional approaches that promote portable rather than inert knowledge.