This paper is concerned with the apparent fact that natural languages build A-bar dependencies either by way of a filler-gap dependency or by way of a resumptive dependency. Its principal empirical goal is to clarify the circumstances under which a choice is made between gaps and resumptive pronouns in A-bar binding constructions in Irish. It is shown that when in competition with gaps, pronouns are disfavored to an overwhelming degree and that they are tolerated only in positions where heightened parsing pressures come to bear. The implications of this finding for the theory and typology of resumption are considered. It is argued that, for Irish and English at least, the relevant parameter makes no reference to pronouns but only to properties of the functional head C.