Public administration has long considered the administrative agency as the core institution shaping action. But specialists in policy implementation, in particular, have suggested that networks spanning multiple organizations may be important phenomena. National legislation from two Congresses is analyzed to determine the kinds of structures explicitly stipulated or encouraged for new or amended programs. The most important questions have to do with the extent to which single-agency or networked (multiactor) structures are used and the relative degree to which intergovernmental versus intragovernmental programs are prominent. The evidence shows that the great majority of legislation requires multiactor structures spanning governments, sectors, and/or agencies; intergovernmental programs are especially prominent; and the multiactor character of the structures has remained relatively constant. These findings carry implications for the study and practice of public administration.