In this study, the conceptual validity of the unified model of personality, postulated by Cloninger (1987) and measured by the Tridimensional Personality Questionnaire (TPQ), is tested in diverse Yugoslav and American societies. The issue of cross-cultural sensitivity of personality studies and the methodology that minimizes distortions and alternative explanations are discussed in detail. Similar personality structures were observed in the Yugoslav and US samples. Differences in novelty seeking (NS, attributed to age differences between the two samples) and harm avoidance (HA, possibly due to long-standing socioeconomic instability in Yugoslavia) are consistent with the unified biosocial theory of personality. Also, the TPQ was found to be psychometrically sound and valid for further research, although some revision in the reward dependence (RD) scale is warranted.