The purpose of this study was to investigate the effectiveness of iconic-based rhythmic instruction on middle school instrumentalists'' ability to read rhythms at sight in the preparation of music for sight-reading. One hundred thirty-one middle school students from 12 randomly assigned bands in the Midwestern United States provided data for a pretest-posttest control-group design. Results from an analysis of covariance revealed that no group obtained a significant difference on the posttest mean scores from the rhythmic performance test after a nine-week period. Because results from individual schools showed considerable variation, other variables were observed to see if they were significant. It was indicated that a significant interaction between the individual school and the pretest to posttest measurement exists. In light of these findings, it is speculated that the key to improving a student''s rhythm-reading ability may be dependent not only on the method, but also on the quality of instructional delivery.