We provide a unified approach to imperfect (monopolistic, Bertrand, and Cournot) competition when preferences are symmetric over a finite but endogenous number of goods. Markups depend on the Morishima elasticity of substitution and on the number of varieties. The comparative statics of free‐entry equilibria is examined, establishing the conditions for markup neutrality with respect to income, market size, and productivity. We compare endogenous and optimal market structures for several non‐CES examples. With a generalized linear direct utility, the markup can be constant and optimal under monopolistic competition, and nonmonotonic in the number of firms under Bertrand or Cournot competition.