This study investigated patterns of acquisition of English and Japanese by a toddler, aged 16-23 months, living in Japan. The child's mother and father are British and Japanese, respectively. The focus of the study was on early grammatical morpheme and transformational rule acquisition as demonstrated in the child's utterances. The study is accompanied by charts of transcribed utterances, and these data are analyzed within the framework of recent language acquisition theory and research. Analyses of sound-meaning and meaningfulness, the ineffectiveness of overt instruction on the child's speech production, morpheme acquisition patterns, and acquisition of certain transformations are reported. Results indicate that regular past tense forms were frequently produced at an early age, in comparison with other English morpheme acquisition studies, but that articles usage appeared to be delayed, possibly due to Japanese deictic acquisition order. Stages for negation, interrogatives, and pronominalization appeared to follow patterns observed by other researchers. Sound-meaning association, movement/change, and meaningfulness appear, in general, to be confirmed as key factors determining when acquisition will occur. Pedagogical implications are discussed. (Author/MSE)