The purpose of this study was to examine how students' perceptions of their teachers' instructional communication behaviors were related to their affective learning in math and science. A survey was used to collect perceptions from 497 ninth-grade students. The following conclusions were yielded from the data: (1) students' perceptions of their math and science teachers' use of clarity and content relevance behaviors, rather than their teachers' use of nonverbal immediacy and disconfirmation behaviors, predicted students' desire to pursue additional study in math and science as well as consider careers in the fields of math and science; (2) students did not perceive meaningful differences in their affective learning between math/science and nonmath/science courses; and (3) students perceived minimal differences between their math/science and nonmath/science teachers' use of instructional communication behaviors. (Contains 5 tables.)