Through a comparison of four carefully selected congresses, this study demonstrates that the current House majority party leadership, when compared to other post-World War II leaderships, is more involved in and more decisive in organizing the party and the chamber, setting the House agenda, and affecting legislative outcomes. An explanation for the emergence of strong leadership is offered and tested. I argue that, during the period under study, the costs and benefits to majority party members of strong leadership changed significantly. The study shows that the 1970s reforms and the 1980s political environment of split control and conflict between a conservative confrontational president and House Democrats greatly increased the difficulty of enacting legislation Democrats find satisfactory and thus increased Democratic committee contingents' and the Democratic membership's need for leadership help. Declining Democratic ideological heterogeneity and decreased opportunities for free-lance policy entrepreneurship reduced the cost of strong leadership to members. The study finds that, both over time and cross sectionally, the likelihood of leadership involvement is greatest when the members most need help and when the costs of the leadership's providing such help are lowest for majority party members and for the leadership itself and, further, that leadership involvement does increase the probability of legislative success.