Three determinants of the factor structures of personality traits are investigated. The 1st, selection of variables, was controlled by using 57 bipolar scales, selected to be representative of common trait terms. In analyses of 7 data sets, variants of the "Big Five" factors were always found. Factor similarities were very strong for the 3 largest factors, which were transformed into general evaluation and 2 descriptive dimensions. As a 2nd determinant, judgments about real people were compared with judgments about the conceptual relations among traits. Factor structures based on the 2 types of judgments are similar, but those based on conceptual judgments tend to be simpler. The 3rd determinant involved the degree of restriction of the sample to evaluatively homogeneous targets. Restriction of range reduced the size of all factors, especially Factor II. Findings from previous studies are integrated within this framework.