The forward effect of testing occurs when testing on previously studied information facilitates subsequent learning. The present research investigated whether interim testing on initially studied materials enhances the learning of new materials in category learning and examined the metacognitive judgments of such learning. Across the 4 experiments, participants learned the painting styles of various artists, which were divided into 2 separate sections (Sections A and B). They were given an interim test or not on the studied paintings of Section A before moving on to study the paintings of different artists in Section B, and then were given a final test on Section B where participants had to transfer what they had previously learned to new exemplars of the studied artists in Section B. In all experiments, transfer performance on Section B was greater when the participants were given an interim test versus no test. The beneficial effect of interim testing was obtained when the final test was presented in cued-recall (Experiments 1 and 2) and multiple-choice (Experiments 3 and 4) formats. Experiments 3 and 4 also indicated that the forward effect of testing was not due to re-exposure to previously studied items but the testing itself. However, the metacognitive measures provided by the participants did not reflect their actual performance, suggesting that the participants were unaware about the beneficial effects of interim testing. Interim testing appears to prepare students to learn better, facilitating not only learning of specific instances but also generalization of that learning.