Self-efficacy and mathematics anxiety have been identified as predictors of mathematics achievement. In the present study, secondary analyses on matrix summaries available from prior published studies were utilized to investigate the contribution that self-efficacy and mathematics anxiety made in mathematics performance. Commonality analyses were invoked for these purposes by investigating data from 4 different studies with 5 samples consisting of students in Grades 6 through college levels. The findings indicated that, in the presence of other variables identified as contributing to mathematics performance mathematics self-efficacy consistently accounted for substantial unique variance in mathematics performance whereas mathematics anxiety consistently did not account for appreciable unique variance in mathematics performance. Therefore, researchers seeking parsimony may wish to include either mathematics self-efficacy or mathematics anxiety in a given model. The findings supported previous path analyses and Bandura's (1997) conclusion that addressing mathematics self-efficacy might help calm mathematics anxiety. (Contains 3 tables and 1 figure.)