The effect of student evaluations of teaching on administrative personnel decisions at the Department of Psychology, University of Western Ontario, was investigated. In addition, the apparent impact of summative student evaluation of teaching upon faculty attitudes and faculty teaching performance was assessed. In the Department of Psychology, undergraduate student evaluations are obtained by a 10-item questionnaire that focuses mainly on expositional skills such as clarity, preparation, and use of examples, and includes a final overall effectiveness item. It was found that: student evaluations of teaching contributed significantly to decisions on faculty salary and tenure, but not to decisions on promotion to full professor; after 12 years of mandatory summative evaluation, faculty members continue to have generally favorable attitudes toward student evaluations of teaching and their use in administrative personnel decisions; and the mean level of teaching effectiveness of the Department of Psychology as a whole has improved substantially over the past 12 years, presumably due, at least in part, to the incentive and selection functions of summative evaluation of teaching. It is suggested that a fully effective teaching evaluation system must include both formative and summative components in order to effect the right combination of feedback, motivation, training, and selection needed to gain faculty acceptance and to produce significant improvement in individual and institutional performance. (SW)