This study examines how a French- and Spanish-speaking child acquired English as a third language. It describes the linguistic experience of the 10-year old boy whose French and Spanish home, school, and playmate environments were changed to English school and playmate environments with French being maintained exclusively at home with the child's father. The dissertation describes a "natural" transition to English with no formal instruction in English being given the child. It is believed that examination of problems encountered by the child on making the linguistic transition, conclusions of the study, and suggestions concerning the learning process will be helpful to elementary school teachers of English as a second or third language. Two major language areas covered in the study are grammar and phonology. The chapter dealing with grammar is divided into two sections: morphology and syntax, and sentence formation. Errors in both grammar and phonology are classified, described, and discussed. A separate chapter on research in bilingualism and language acquisition is included. (RL)