ThispaperteststherelationshipbetweenaveragereturnandriskforNewYorkStockExchangecommonstocks.Thetheoreticalbasisofthetestsisthe"two-parameter"portfoliomodelandmodelsofmarketequilibriumderivedfromthetwo-parameterportfoliomodel.Wecan-no!rejectthehypothesisofthesemodelsthatthep