The relationship between self-esteem deriving from both personal and social identity and comparisons at both interpersonal and intergroup level was examined. Participants took part in individual and group brainstorming tasks which they later had the opportunity to evaluate. In the case of the individual task, participants' own solutions were judged in conjunction with solutions provided by a member of their ingroup and a member of the outgroup. For the group task, the ingroup solution was compared with an outgroup solution. Both personal and collective self-esteem were found to influence these ratings, but in different ways. In terms of intergroup comparisons, participants with high personal self-esteem (PSE) showed greatest ingroup bias. In contrast, this same effect was associated with low public collective-self esteem (CSE), that is, people who felt that their group was viewed negatively differentiated most strongly. Furthermore, this opposition of the effects of PSE and CSE also applied to the interpersonal comparisons. Participants with high PSE self-enhanced relative to participants with low PSE, while the reverse pertained for CSE scores. Participants with low private CSE rated both their own and the ingroup member's solution more positively than the outgroup solution. An analysis is presented which explains these effects in terms of threat experienced as a result of incongruency between comparative context and optimal identity enhancement strategies. Copyright © 1998 John Wiley & Sons, Ltd.