This study examined the temporal and dynamic nature of students' self-regulatory processes while learning about the circulatory system with hypermedia. A total of 74 undergraduate students were randomly assigned to 1 of 2 conditions: independent learning or externally assisted learning. Participants in the independent learning condition used a hypermedia environment to learn about the circulatory system on their own, while participants in the externally assisted condition used the same hypermedia environment, but were given prompts and feedback from a human tutor during the session to facilitate their self-regulatory behavior. Previously published pretest-posttest shifts toward more mature understanding of the circulatory system indicate that the externally assisted condition leads to greater learning. The present article uses think-aloud data during learning to explore process issues in light of models of self-regulated learning and conditions of engagement that may affect those processes. Results indicate that access to a human tutor influences the deployment of regulatory processes, intervals of use, and temporal dependencies. For example, there is significantly more planning during the final time interval of the learning session in the externally assisted condition; students in both conditions deploy more learning strategies in the first and second time intervals, compared to the last two time intervals. Additionally, in the externally assisted condition participants were more likely to shift from planning to monitoring and less likely to shift from learning strategies to planning. We discuss theoretical, conceptual, and methodological issues pertaining to these results, as well as implications for future research and the design of adaptive hypermedia systems. (Contains 2 figures, 5 tables, and 3 footnotes.)