This paper reports on an empirical study that examined knowledge of eventive and stative passives in the L2 Spanish grammar of L1 speakers of English. Although the two types of passive exist in English, the difference between them is not signaled in any specific way. In Spanish, in contrast, the distinction is marked by the choice of copula: ser is used to form eventive passives, estar for statives. Researchers agree that the two copulas, both of which translate as English “to be”, differ in relation to aspect: estar is perfective while ser is not marked for aspect (Schmitt, 1992). The question was whether L2 learners would be able to acquire the aspectual difference of the copulas and apply it to the formation of the passives. Two main tests were used, a Grammaticality Judgment Task and a Sentence Selection Task. The Grammaticality Judgment Task examined properties of the passives related, among other things, to aspect and agentivity. The Sentence Selection Task focused on the interpretation of the subject: only the subject of ser can be interpreted as generic. Although the learners in general distinguished between grammatical and ungrammatical sentences, they had not acquired the restriction on subject interpretation. These results are explained in terms of interfaces.