This paper considers how government size responds to a change in the influence of interest groups. First, an election model is developed that has an equilibrium and in which interest groups have unequal influence. The authors then show that an increase in a group's influence per se does not cause government size to increase but does cause its size to increase when the government (1) cannot change tax shares or (2) provides a good benefiting one (untaxed) group, whose sole interest is in maximizing its consumption of the good. The paper concludes with a discussion of some of the normative implications.