To determine the effects of educational experiences on the knowledge of and attitudes toward mental retardation, 279 newly admitted graduate students and 288 graduating students in seven schools of social work completed a personal data sheet, semantic differential rating scales, a knowledge inventory, and a client preference rank order scale. Subjects having little experience with the retarded rated them less favorably on all 21 semantic scales (p.01) while subjects with retarded siblings or relatives tended to be more favorable and knowledgeable. Students had a general image of the retarded based on characteristics of the severely and moderately handicapped; the retarded ranked sixth in preference among 10 client groups. Client preference changes occurred more often in high exposure schools but rank ordering of client groups remained basically unchanged. Students in field instruction placements serving the retarded were superior in knowledge (p=.05) and showed greater attitude changes and greater extremes in client preference (predominantly in a positive direction). Conclusions were that the introduction of content on mental retardation in social work curriculum does not materially affect knowledge and attitudes. (RJ)