The purpose of this paper is to examine the usefulness of factor analysis in developing and evaluating personality scales that measure limited domain constructs The approach advocated follows from several assumptions that a single scale ought to measure a single construct, that factor analysis ought to be applied routinely to new personality scales, and that the factors of a scale are important if it can be demonstrated that they are differentially related to other measures A detailed study of the Self-Monitoring Scale illustrates how factor analysis can help us to understand what a scale measures A second example uses the self-esteem literature to illustrate how factor analysis can clarify the proliferation of scales within a single content domain Both examples show how factor analysis can be used to identify important conceptual distinctions Confirmatory techniques are also introduced as a means for testing specific hypotheses It is concluded that factor analysis can make an important contribution to programmatic research in personality psychology