This study analyzes the relationship between students' online work habits and academic performance. We utilize data from logs recorded by a course management system (CMS) in two courses at a small liberal arts college in the U.S. Both courses required the completion of a large number of online assignments. We measure three aspects of students' online work habits: timeliness, regularity, and intensity. We find that students with a high overall GPA and a high grade in the course work on assignments early and more regularly. We also find that the regularity of work habits during the first half of the term predicts grade in the course, even while controlling for the overall GPA. Overall, however, the marginal predictive power of CMS data is rather limited. Still, the fact that high achieving students show vastly different work habits from low achieving students supports interventions aimed at improving time-management skills.