This paper aims to analyse in what way Brazilian Portuguese bare plurals affect the aspectual structure of a sentence whose VP is headed by an achievement verb. In order to achieve this goal, we will study the interaction of these VPs composed by achievements with aspectual verbs. We will argue that: a) achievements do not have the property of S-cumulativity (Rothstein, 2004), b) aspectual verbs select as complements predicates which have the property of S-cumulativity, and c) the property of S-cumulativity is the semantic contribution given by bare plurals to the aspectual structure of the sentence. Based on these ideas, we predict that the sentences formed by the combination of an aspectual verb and a VP whose structure is [achievement verb-NP] will be grammatical only if the NP complement of the achievement verb is a bare plural. This is the way by which this constituent will satisfy the selectional constraints imposed by the aspectual verb. This paper was presented at the Workshop "Bare Plurals and Indefinites", in Florianópolis, Brazil, June 2009. We thank the audience for comments and criticisms. We are especially grateful to Susan Rothstein for helpful explanations about her theory and to two anonymous JPL reviewers whose comments and suggestions helped us to improve the first draft. Finally, we would like to thank the financial support received from the following agencies: CAPES/COFECUB (grant 2793/09-1), FAPESP (grant 07/58451-7), CAPES/PDEE (grant 2369/09-5) and CNPq (grant 140133/2006-2). All errors and inadequacies are ours.