Despite the popularity of diversity training in corporate America, a lack of systematic evaluation has left managers with little guidance on how to design effective diversity training programmes. In this research, we examine how training group composition and trainee experience interact to influence the effects of diversity training on cognitive, affective, and behavioral outcomes. Results indicate that trainees with prior experience with diversity training responded most positively to training groups homogeneous with respect to racioethnicity and nationality; trainees without prior experience with diversity training were generally unaffected by training group composition. The implications of these findings for the design of diversity training programmes in organizations and future research on diversity training are discussed. Copyright © 2001 John Wiley & Sons, Ltd.