This chapter reports the results of a 20-year longitudinal study of how American unions have adapted their internal administrative practices to meet the significant external challenges they face. In previous scholarly work, researchers have reported that the administrative practices of American unions were far more informal, ad hoc, and political than those of business, government, and other nonprofit organizations. The authors' 2010 survey asked US-based national and international unions to provide data concerning their internal administrative practices. The results were compared with findings from similar surveys conducted in 1990 and 2000. The results of these surveys indicate a steady increase in unions' adoption of more formal personnel policies, budget practices, strategic planning processes, and efforts to evaluate planned activities over the 20-year period studied. They also indicate that unions increasingly recruit individuals meeting college, technical, and professional qualifications. Taken together, the results suggest a recognition on the part of many unions that adapting their internal administrative practices to the new realities they face is a fundamental and a necessary part of any effort at organizational renewal.