Previous taxonomies of personality traits have been lexical in nature and have been concerned primarily with the meaning of adjectives in personality description. The taxonomy presented in this article employed personality scales as the units to be classified and was guided by theoretical, rather than lexical, considerations. A priori distinctions among different domains of trait-descriptive terms identified a distinctive domain of interpersonal traits within which a preliminary conceptually-based taxonomy was developed. The Interpersonal Adjective Scales (IAS) were constructed to provide geometrically precise semantic markers of that domain in the form of a circumplex model organized around the orthogonal coordinates of dominance and nurturance. In the course of a decade of research, some 172 personality scales were classified with reference to the IAS by computational procedures described in detail. Advantages and limitations of the current geometric taxonomy of personality scales are discussed, and future research directions are indicated.