Leadership researchers and theorists alike have come to recognize that the critical tasks of senior level leaders are quite different from the critical leadership tasks of individuals occupying lower level leadership positions. Departing from the bulk of prior research on individual differences in leadership effectiveness which focused on differences in managerial "style" or on component decision making processes, this study explores conceptual capability as a predictor of leadership success. Leader differences in conceptual capacity were examined in a sample of 44 war college students. Replicating earlier findings, war college students demonstrated a range of conceptual capability, despite the fact that they had all been highly successful leaders at the direct leadership level. Interview based ratings of breadth of perspective and conceptual work capacity were demonstrated to have acceptable levels of interrater reliability. Despite clear conceptual and methodological differences, the two measures of conceptual capability were found to be correlated. Student's conceptual work capacity, but not their breadth of perspective, was found to be positively related to war college instructor ratings of students' strategic thinking skill but not their peer popularity. (Contains 31 references.) (RB)