The perceived relation between assigned student grades and instructor evaluations of teaching has been the subject of much debate, though few laboratory studies have been conducted with adequate controls. Marsh and Roche suggested that experimental field studies may be a particularly promising avenue for further analyses of this relation. The authors report two multiple-session studies that used videotaped instruction and artificially set class quiz averages. The first study involved administering multiple-choice quizzes over the videotaped lecture; the second study utilized essay quizzes. The results suggest that grades affect evaluations only when using subjective testing methods. (Contains 1 figure, 1 table, and 2 notes.)