Due to the recognition of the centrality of the lexicon for SLA theory (see the 1987 thematicissue of SSLA, edited by Susan Gass), the last few years have witnessed an increasedinterest in understanding lexical knowledge. As Gass (1999) reminded us, learning vocabulary in asecond 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 syntacticallyconstrained. The present issue provides a natural sequel to the 1999 SSLA thematicissue, “Incidental L2 Vocabulary Acquisition,” by addressing some of the questionsraised in that volume, in particular the questions related to the intimate relationship betweensyntax and semantics at the lexical interface. This issue is devoted to the L2 acquisition of verbmeaning and argument structure crosslinguistically, and it explores in detail the nature of linguisticsystems that L2 learners acquire in this particular domain. The six central articles offer a coherentapproach to the topic, using linguistic theory to help us understand the characteristics of learnergrammars. Until recently, linguistic approaches to SLA have placed a strong emphasis onunderstanding the acquisition of functional categories, for example, and the acquisition of thelexicon has received less attention. Understanding how the lexico-syntactic interface is mentallyrepresented, and how it evolves during the second language acquisition process, is crucial fordeveloping an adequate theory of L2 knowledge in general, as well as for informing theories ofthe lexicon.