Due to the recognition of the centrality of the lexicon for SLA theory (see the 1987 thematic issue of SSLA, edited by Susan Gass), the last few years have witnessed an increased interest in understanding lexical knowledge. As Gass (1999) reminded us, learning vocabulary in a second language is a complex task that involves much more than learning sound-meaning pairings; it also involves learning how lexical information is morphologically expressed and syntactically constrained. The present issue provides a natural sequel to the 1999 SSLA thematic issue, “Incidental L2 Vocabulary Acquisition,” by addressing some of the questions raised in that volume, in particular the questions related to the intimate relationship between syntax and semantics at the lexical interface. This issue is devoted to the L2 acquisition of verb meaning and argument structure crosslinguistically, and it explores in detail the nature of linguistic systems that L2 learners acquire in this particular domain. The six central articles offer a coherent approach to the topic, using linguistic theory to help us understand the characteristics of learner grammars. Until recently, linguistic approaches to SLA have placed a strong emphasis on understanding the acquisition of functional categories, for example, and the acquisition of the lexicon has received less attention. Understanding how the lexico-syntactic interface is mentally represented, and how it evolves during the second language acquisition process, is crucial for developing an adequate theory of L2 knowledge in general, as well as for informing theories of the lexicon.