In an experience-sampling study, we tested the influence of goal progress on subsequent effort toward that goal among persons with bipolar disorder (BD) and among control subjects without BD. We hypothesized, overall, that unexpectedly low progress toward a goal would lead to an increase in subsequent effort toward that goal, and unexpectedly high progress would lead to a decrease in effort (permitting effort to be shifted to another goal). Drawing on literature relating BD to elevated goal-approach sensitivity, we hypothesized that persons with BD would be less responsive to unexpectedly high progress than would control subjects. Participants answered questions three times a day, for 21 days, about three goals. The results of the study confirmed our overall hypothesis. In addition, although the reactions of persons with BD did not differ from the reactions of control subjects after lower-than-expected goal progress, persons with BD decreased effort toward goals significantly less than did control subjects after better-than-expected goal progress.