Two experiments exploring the structure of bilingual memory as a function of second language proficiency and distance between the two languages are reported. Experiment 1, manipulating categorization of word lists, explored bi-directional translation in Japanese-English, two distantly related languages, while Experiment 2 did the same using Japanese- Korean as more closely related languages. The findings, indicating that asymmetry of translation occurs only in more proficient Japanese-English bilinguals (Expt. I), while occurring at both levels of proficiency Japanese-Korean bilinguals (Expt. 2), provide support for the asymmetric model of links between lexical and conceptual systems of bilingual memory (Kroll & Stewart, 1994). They demonstrate that the functional architecture of the model alters with changes in second language proficiency. The findings also indicate that the relationship between the two languages of a bilingual plays an important role in the nature and lexical organization of the mental lexicon.

Key words: translation asymmetry, bilinguals and second language proficiency