The question of the correct form of the Corinthian entablature presented substantial problems for Renaissance architects, since Vitruvius’s account was unsatisfactory, while Roman ruins provided an extensive variety of examples. In the first book of his I quattro libri dell’architettura Palladio copied the morphology of the canonical Corinthian entablature from Vignola, but recommended a different set of proportions. In order to establish the origin of these alternative proportions, in this paper I analysed their relationship to the proportions of the Corinthian entablatures from Roman temples as Palladio presented them in his archaeological surveys in the fourth book of I quattro libri.