This study tested hypotheses on the relationship between achievement of proficiency in spoken Japanese and the variables of ease of adjustment to life in Japan; effects of childhood multilingualism, musical background, and previous level of formal education; and deliberately delaying the introduction of kanji (Chinese ideographs) into intensive language study materials. A special 79 item questionnaire was completed by 654 active missionaries who had finished two years of language study. Language proficiency subscales were developed to cover reading and writing, speaking, exposure to linguistic stimuli, developed aptitude, cosmopolitanism, aural dependency (reliance on learning by ear), and statisfaction with the curriculum and other program elements. Rate of language learning was significantly and positively related to childhood multilingualism, sensitivity to semantic differences, and ease of adjustment, but not to the other hypothesized variables. (LY)