Many political scientists like institutions, in particular exog- enous institutions, which guide and constrain actions and allow scholars to concentrate more narrowly on behaviors within well-defined settings. For the interest groups subfield, institutions tend to be more mercurial than those in other areas of American politics. For instance, fundamental aspects of Congress may be institutionalized, but groups and lobby- ists come and go. The environment of interests is ever changing. Characterizing the interactions between legislators and lobbyists is made more difficult because of the lack of clear institutional structures that guide or constrain behav- iors. The iron triangle concept was powerful and meaningful because it provided at the least a loose framework for the analysis of legislator-lobbyist interactions. Kevin Hula's new book follows the reasoning of Hugh Heclo and William Browne, who argue that the iron triangle concept is outdated and inappropriate. That convenient metaphor suggested an informal institutional structure that is simply no longer appropriate. Without the iron triangle, what can fill the void?