In this paper, we investigate Chinese L2 learners' knowledge of two grammatical constraints in Vietnamese: the first, a constraint on the aspectual interpretation of accomplishment predicates, the second pertaining to alternations in the position of embedded subjects in mono-clausal lam causatives. Whereas the former constraint is shared by Vietnamese and Chinese, the two languages differ with respect to the latter. The results of three judgment tasks provide statistically reliable support for the idea that L2 interlanguage grammars are not ultimately limited by Ll patterns; given the absence of explicit teaching and only limited exposure to relevant structures, it is suggested that learners' performance may be guided by UG information
