One of the interesting possibilities suggested by the development of interlanguage studies is a correlation between the L1/L2 variation and the distinction between language-universal/language-particular constraints governing the variation within a language system. If there were a language-universal constraint such that all the (known) languages conform to it, then one would expect that interlanguage, as a language system in itself, should conform to such a constraint as well. This paper takes up the zero-marking of an accusative case marker o in Japanese to explore the possibility mentioned above. Zero-marking of o, which is most sensitive to the adjacency between the object NP and the verb (a language-particular constraint), has at least one constraint that is known to be a language-universal : the distinction between the lexical NP and the pronoun for the object NP, with the pronoun significantly disfavoring zero-marking. This is easily explainable as a reflection of a language universal such that a language with an overt case-marking system should case-mark the pronouns, but not necessarily the lexical NPs. Using a corpus of transcribed OPI interviews with Chinese and Korean speakers, I collected relevant accusative constructions to see if the variable zero-marking by the L2 speakers is accountable by the language-particular/ universal factors. The result shows that : (1) the form of NP showed up as the significant factor in predicting the zero-marking by the L2 speaker and (2) the difference between the pronoun and the lexical NP, also was as expected, with pronoun disfavoring zero-marking. The result clearly shows that at least in the early and mid stage of L2 acquisition, the interlanguage system reveals language-universal constraint, in this case the implicational relationship between the case-marking on NP and pronoun
