This paper explores the extent and character of interest group influen
ce on legislative policy in a model of decision making under incomplet
e information. A committee may propose an alternative to a given statu
s quo under closed rule. Policies are related to consequences with ex
ante uncertainty. An interest group is able to acquire policy-relevant
information at a price and has access to legislators at both the agen
da-setting stage and the vote stage. Lobbying is modeled as a game of
strategic information transmission. The price of information is itself
a private datum to the group, and legislators cannot observe whether
the group elects to become informed. If the group is informed, then it
s information is likewise private. Among the results are that not all
informed lobbyists choose to try to influence the agenda directly; tha
t there can coexist influential lobbying at both stages of the process
; and that while informative agenda stage lobbying is generically infl
uential, the same is not true of voting stage lobbying.