Student ratings of college professors play an important role in many employment decisions. One factor strongly associated with student ratings is teacher expressiveness. A study was conducted to explore the effects of teacher expressiveness, teacher sex, and student sex on student ratings of their instructor, student perceptions of their instructor's gender-linked characteristics, and on student achievement. Forty male and 40 female undergraduate students viewed a videotape of either a male or female instructor acting either expressively or nonexpressively. Students then completed a student rating form, the short form of the Bem Sex Role Inventory to rate the instructor's personality, and a short multiple-choice test on lecture content. The results revealed that expressive instructors received the most positive student ratings on all measures, although expressiveness interacted with teacher sex on the rating of scholarship such that the expressive male instructor was rated the lowest. Expressiveness also interacted with both teacher sex and student sex on achievement scores. Student-perceived teacher sex-typing may partially explain the effect of expressiveness on student ratings. (Author/NB)