Students' confidence calibrations on quizzes taken individually and again in structured learning groups were examined. Under conditions of weekly feedback on accuracy and confidence, students working as individuals and in groups were hypothesized to improve not only their accuracy, but also their calibration of confidence. Findings were based on individual and group assessments of learning over a semester on actual course material. Data include confidence ratings from 32 undergraduates (13 males and 19 females) and their 10 learning groups on a series of 11 weekly quizzes. Within groups, students improved their accuracy, but they did not appropriately adjust their confidence judgments. The benefit of improved accuracy in groups came at the cost of increased confidence for wrong answers. Neither frequent feedback nor assignment to structured learning groups appears effective at improving students' calibration of confidence, and in particular cases, either may even make it worse. Five tables and seven figures present study findings. There is a 12-item list of references. (SLD)