This experimental study examined the causal effects of transformational and transactional leadership and the mediating role of trust and value congruence on follower performance. A total of 194 student participants worked on a brainstorming task under transformational and transactional leadership conditions. Leadership styles were manipulated using two confederates, and followers' performance was evaluated via three measures—quantity, quality, and satisfaction. Results, based on path analyses using LISREL, indicated that transformational leadership had both direct and indirect effects on performance mediated through followers' trust in the leader and value congruence. However, transactional leadership had only indirect effects on followers' performance mediated through followers' trust and value congruence. Implications of these results for future research on leadership are provided. Copyright © 2000 John Wiley & Sons, Ltd.