Much research contrasts self-reported personality traits across cultures. We submit that this enterprise is weakened by significant methodological problems (in particular, the reference-group effect) that undermine the validity of national averages of personality scores. In this study, behavioral and demographic predictors of conscientiousness were correlated with different cross-national measures of conscientiousness based on self-reports, peer reports, and perceptions of national character. The predictors correlated strongly with perceptions of national character, but not with self-reports and peer reports. Country-level self- and peer-report measures of conscientiousness failed as markers of between-nation differences in personality. Copyright © 2008 Association for Psychological Science.