A meta-analysis of the transformational leadership literature using the Multifactor Leadership Questionnaire (MLQ) was conducted to (a) integrate the diverse findings, (b) compute an average effect for different leadership scales, and (c) probe for certain moderators of the leadership style-effectiveness relationship. Transformational leadership scales of the MLQ were found to be reliable and significantly predicted work unit effectiveness across the set of studies examined. Moderator variables suggested by the literature, including level of the leader (high or low), organizational setting (public or private), and operationalization of the criterion measure (subordinate perceptions or organizational measures of effectiveness), were empirically tested and found to have differential impacts on correlations between leader style and effectiveness. The operationalization of the criterion variable emerged as a powerful moderator. Unanticipated findings for type of organization and level of the leader are explored regarding the frequency of transformational leader behavior and relationships with effectiveness.