This essay critically reviews research published in the last decade th
at explores how lobbyists and interest groups influence the actions of
the U.S. Congress. The research is extensive and contains a rich, but
often conflicting, set of findings about the influence of interest gr
oups. The purpose of this essay is to inventory, review, and critique
this research in ways that convey as clearly as possible the status of
our current understanding of the nature and level of interest group i
nfluence in the U.S. Congress.