This monograph presents a theoretical and empirical study of the Spanish and the Portuguese Present Perfect (PP). The innovative claim is that the two tense forms operate in the field of tension between temporal quantification and temporal reference. Based on this approach, it presents the first in-depth study that explicitly takes into account the level of discourse. The following questions are investigated: How do the Spanish and the Portuguese PP interact with discursive factors, such as adjacent tense forms? What kind of discursive meaning do they generate? Which diachronic trends do their discourse functions reveal? It is argued that while the Spanish PP tends to a referential drift (traditionally labelled as an aoristic drift), the Portuguese PP tends to preserve and specialize its quantificational meaning. The book is of interest to all those working on the Present Perfect or generally in the field of tense and aspect in discourse.