Most metacognition research has focused on aggregate judgments of overall performance or item-level judgments about performance on particular questions. However, metacognitive judgments at the category level, which have not been as extensively explored, also play a role in students' study strategies, for example, when students determine what topics to study for an exam. We investigated whether category learning judgments (CLJs) were sensitive to differences in the difficulty of general knowledge categories. After either studying or being tested on facts from several categories (e.g., Shakespeare, Astronomy), participants estimated the likelihood that they could correctly answer new questions from those categories on a later test (i.e., they made CLJs). Results of two studies showed that CLJs were sensitive to differences in category difficulty. Further, participants gave lower or more conservative CLJs when they took an initial test as compared to studying questions from the categories. Results are discussed in terms of the value and relevance of CLJs both in educational settings and in theories of metacognition.