A number of studies have shown that adult L2 learners come to know subtle grammatical properties of the target language which are not present in the L1 nor salient in the input (e.g., Dekydtspotter and Sprouse, 2001; Kanno, 1999; Schreiber and Sprouse, 1998). The present study, a partial replication of Bruhn de Garavito (1999a, 1999b), investigates the L2 acquisition of Spanish reflexive passives and reflexive impersonals by French- and English-speaking adults at an advanced level of proficiency. The L2 acquisition of Spanish reflexive passives and reflexive impersonals by native French and English speakers instantiates a potential learnability problem, because (1) the constructions are superficially very similar (se V DP) but display distinct idiosyncratic morphological and syntactic behavior; (2) neither exists in English, and the reflexive impersonal does not exist in French; and (3) differences between the two are typically not subject to explicit instruction. Participants (13 English, 16 French, and 27 Spanish speakers [controls]) completed a 64-item grammaticality-judgment task. The mean grammaticality judgments show that L2 learners could in general differentiate grammatical from ungrammatical items, but they performed significantly differently from the control group on most sentence types. The participants' accuracy rates, however, indicate that most L2 learners failed to provide the appropriate contrasts between grammatical and ungrammatical items. Test items involving [+animate] DPs preceded or not by the object-marking preposition 'a' were particularly problematic, as L2 learners judged them either as grammatical or marginal. These results confirm that the L2 acquisition of Spanish reflexive passives and reflexive impersonals by French- and English-speaking adults instantiates a learnability problem, not yet overcome at an advanced level of proficiency.