The fact that the specifier of T0 is subject both to the Extended Projection Principle (EPP) and to the Empty Category Principle (ECP) has remained an unexplained accident within Government-Binding Theory. I propose a principled account of this correlation. The EPP is a selectional requirement of functional heads (e.g., T, Top, C) that applies at PF—an instance of p-selection for an overt element. Like all selectional requirements, it applies to the head of the selected phrase, explaining why null heads cannot appear in EPP positions (thus deriving certain representational ECP effects). A wide range of empirical results follow, all unified by the exclusion of null-headed phrases from EPP positions: subject-object asymmetries in the distribution of bare nouns in Romance and sentential complements; failure of certain adjuncts to occur in clause-initial position; resistance of indirect objects to Ā-movement; and phonological doubling of heads of fronted categories. I argue against the agreement/checking view of the EPP and show that only the selectional construal allows a natural explanation of its puzzling properties.