When people judge their learning of items across study-test trials, their accuracy in discriminating between learned and unlearned items improves on the second trial. We examined the source of this improvement by estimating the contribution of three factors-memory for past test performance (MPT), new learning, and forgetting-to accuracy on trial 2. In Experiment 1, during an initial trial, participants studied paired associates, made a judgment of learning (JOL) for each one, and were tested. During the second trial, we manipulated two variables: when the JOL was made (either immediately before or after studying an item) and whether participants were told the outcome of the initial recall attempt on trial 1. In Experiment 2, the same procedure was used with a 1-week retention interval between study and test on trial 2. In both experiments, JOL resolution was higher on trial 2 than on trial 1. Finegrained analyses of JOL magnitude and decomposition of resolution supported several conclusions. First, MPT contributed the most to boosts in JOL magnitude and improvements in resolution across trials. Second, JOLs and subsequent resolution were sensitive to new learning and forgetting, but only when participants' judgments were made after study. Thus, JOLs appear to integrate information from multiple factors, and these factors jointly contribute to JOL resolution.