What effect does the professional character of a legislature have on the power of its legislative leaders? Despite legislative scholars' desire to better understand both institutional professionalism and leadership power, few empirical studies have explored the relationship between these two important elements of American state legislatures. Moreover, of the research that has been conducted, little effort has been made to understand the impact of professionalism on leadership from a theoretical perspective. This article expands our understanding of legislative professionalism and leadership while testing three theoretical models of legislative organization. I examine the effect of professionalism and several control variables on the influence of state house leaders in 38 non-southern states in 1981 and 1995. Contrary to the fears of some analysts, I find that more professional state legislatures tend to have more powerful leaders. These results provide support for a partisan model of legislative organization.