Student ratings of instruction are widely used as a basis for personnel decisions and faculty development recommendations. This digest discusses concerns about the validity of student ratings and presents a case for their use in teacher evaluation. There are several strong arguments for using student ratings to evaluate teachers. Students are in a unique position to rate their own increased knowledge and comprehension, and they are able to rate aspects of instructor competence and attitude. Nine possible lines of argument for the validity of student ratings are summarized, but it is noted that student ratings become invalid if the rating form used is not appropriate for the data collection required. Several points in form design are described, and errors to be avoided are noted. Student ratings must be considered carefully in the context in which they are given, and they cannot be the only source for teacher evaluation. (Contains 4 references.) (SLD)