This document provides an outline on monopolistic competition and oligopoly. It begins by explaining where monopolistic competition fits between perfect competition and monopoly. It then discusses the assumptions and characteristics of monopolistic competition in both the short run and long run, including excess capacity, product differentiation, and efficiency. The document next covers the assumptions and concentration ratios used to define oligopoly markets. Finally, it summarizes two models used to analyze oligopoly - cartel theory and game theory, using the prisoner's dilemma example.