Random parallel reading comprehension tests in Japanese and English were administered to a sample of native Japanese students enrolled in intensive English instruction. The students had been placed at three different levels of English language proficiency based on an independent proficiency assessment measure. Evidence for a threshold competency ceiling at which first language reading abilities transferred to second language reading abilities was found. At the highest proficiency level, those readers scoring high on the first language reading test also systematically scored high on the second language reading test. The findings indicate that studies of this nature must be conducted with subjects at different proficiency levels. In addition, evidence that imperfect knowledge of the second language can cause difficulty in second language reading emerged. Pedagogical implications are discussed. (Author/MSE)