A few large companies, and a few small companies. The competition still exists amongst these firms in terms of product/ service, etc. What one firm does will impact the others. Entry and exist into these industry is difficult. Why? Because economies of scale has been established all ready...making it VERY expensive for other firms to enter into the industry. ---A branch of oligopoly is called a Cartel--- Same attributes of a oligopoly, however, there is now cooperation within the firms (cooperation with output, marketing, distribution and marketing).