In this study, the robustness of the Big Five personality factors in adolescents' self-ratings and peer nominations was investigated. Data were obtained on 2,001 adolescents attending secondary school (885 girls; 1,116 boys; M age = 14.5 years). Exploratory and confirmatory factor analyses on the self-ratings confirmed the Big Five personality factors. In contrast, exploratory analysis on the peer nominations revealed five different factors: Aggression-Inattentiveness, Achievement-Withdrawal, Self-Confidence, Sociability, and Emotionality-Nervousness. It is suggested that peers evaluate group members not in terms of their personality but in terms of their group reputation. Peer evaluations contributed substantially to the prediction of peer acceptance and rejection; the Big Five personality factors based on self-ratings did not.