Arizona v. Maricopa County Medical Society, 457 U.S. 332 (1982), was a U.S. Supreme Court case involving antitrust law.

A society of doctors in Maricopa County, Arizona, established maximum fees that their members could claim for seeing patients who were covered by certain health insurance plans.

The society tried to rebut the state's charges by claiming that the maximum-fee arrangement was necessary to allow doctors to see these patients, and therefore generated economic benefits.

On appeal, the Supreme Court rejected this defense, saying that price fixing was not truly necessary here: the society could have used insurance to pool their risk.

Arizona filed a complaint against MCMS in Federal District Court, alleging that they were engaged in an illegal price-fixing conspiracy in violation of the Sherman Antitrust Act.