Error correction is a classroom activity that rarely interests the students. When students are given back their written tests they are interested in the mark earned--not the errors made. This case study used cooperative learning as a technique for correcting students' errors in order to motivate them, raise their attention, and encourage them to learn from each other. Two parallel classes in an Italian secondary school were involved in this experiment: one was corrected through traditional methods, the other through cooperative learning, so that data could be compared over time and differences (if any) highlighted. In particular, this paper presents the students' scores in a pretest, test, and post-test; the students' opinions about the activity; and the communicative exchanges, which occurred within cooperative groups. Cooperative learning applied to error correction, which is a rather new match for research, seems to be effective: the students who experienced the cooperative activity on error correction had better results than the ones corrected through traditional methods, especially in the long term (six weeks after the correction activity). The cooperative correction activity was also enjoyed and perceived as useful by the students themselves. (Contains 2 tables.)