ABSTRACT:This paper is based on a doctoral thesis, The phonological influence of English upon Yoruba, prepared at the Department of Phonetics and Linguistics, University College London. Extensive fieldwork was carried out in Nigeria and London, at the end of which a large corpus of English loanwords was compiled. Subjects for the investigation were carefully selected to include a monolingual control group whose usage of loans cannot be attributed to code‐switching. The limits of the areas of phonological influence of English on Yoruba are shown, and these influences, how they were introduced into the language, and their subsequent diffusion into the phonological system, are described. For each influence, an attempt is made to detail phonetic/linguistic motivations where they exist. Finally, theoretical statements are made about phonological systems in contact, especially where the languages are non‐contigu