This research investigated the relationships among test performance, anxiety, and the quality of interaction during collaborative testing of college students. It also explored which students are most likely to benefit from collaborative testing. It was randomly determined whether a student would take each of six examinations alone or with a partner. Collaborative testing resulted in higher scores than individual testing for a significant number of students, conferring an advantage of 3.83%. Test performance was positively correlated with quality of interaction. Students with higher levels of test anxiety were most likely to benefit from collaborative testing and to experience the greatest test anxiety reduction. (Contains 5 tables.)