This chapter deals with the topic of whether L2 speakers are able to develop a nativelike sensitivity to morphosyntactic violations in sentence processing. It is an issue closely related to the more general question of whether L2 learners, particularly adults, are able to develop a nativelike competence in the area of morphosyntax of a non-native language. The chapter begins with a discussion of the methodological issues underlying this research. It is followed by a review of both behavioral and electrophysiological evidence on the topic, and a discussion of some potential explanations for the conflicting findings obtained in this area. The chapter ends with a theoretical proposal for explaining the morphological congruency effect and a summary of related research evidence.