There has been considerable debate as to whether course evaluations are valid measures of teaching quality, or whether students instead reward tutors who give them high grades and assign low levels of work. To assess the factors that influence course evaluations, we measured university students' achievement goals and expectations at the beginning of the semester and also obtained information on grades and workload. Although grades and course difficulty did have a small influence on end-of-semester course ratings, structural modelling revealed that ratings were largely determined by how much students enjoyed or felt stimulated by the course content, which in turn depended on the perceived quality of teaching. Students with a mastery goal were more likely to look forward to the course, and this also contributed to positive course evaluations, but the effect was small. Overall, the results suggested that by far the largest determinant of student evaluation of courses is the quality of the teaching. (Contains 3 figures, 2 tables, and 2 notes.)