In light of repeated prescriptions for theory-driven prediction of job performance (Guion & Gottier, 1965; Tett, Jackson, Rothstein, & Reddon, 1999), the complexity of the manager's role calls for a comprehensive performance taxonomy more detailed than those offered previously. Review of recent discussion of the fidelity-bandwidth tradeoff (e.g., Hogan & Roberts, 1996; Ones & Viswesvaran, 1996) and the need for greater articulation of job performance (Campbell, 1994; Murphy & Shiarella, 1997) raise important issues regarding construct specificity in considering managerial behavior. None of 12 earlier managerial performance taxonomies (e.g., Borman & Brush, 1993; Tornow & Pinto, 1976; Yukl & Lepsinger, 1992) offers adequate specificity for meeting key research challenges. A "hyperdimensional" taxonomy of managerial competencies, derived from the earlier models and developed using unique methods, was subjected to content validation by expert review in 3 studies. In the first 2, a total of 110 Academy of Management members sorted 141 behavioral elements into 47 competencies with average hit rates of 68% and 85%, respectively. Results directed model refinements, including addition of 6 competencies. In Study 3, 118 subject matter experts sorted behaviors into targeted competencies in a more rigorous task with an average hit rate of 88.5%. Findings support the model's content validity, its continued development, and most importantly, the pursuit of specificity in understanding and predicting managerial behavior.