This research empirically examined student behavior in online courses and its relationship to persistence and achievement across fields. Eight variables descriptive of student behaviors online were measured for 1) frequency and 2) duration of participation. Twenty-two courses were grouped into three broad fields: English and Communication; Social Sciences; and Math, Science, and Technology. The descriptive data revealed significant differences in student online participation, persistence, and achievement across the fields. Multiple regression analyses were used to evaluate how well student participation measures predicted achievement. Depending on the field, different portions of the variability in achievement were accounted for by student participation measures. (Contains 1 figure and 7 tables.)