After showing that standardisation processes in spoken and written usage in Jamaica must be seen as distinct from each other, the paper focuses on the role of the creole substrate in the formation of the emergent written standard in Jamaica. The approach is corpus-based, using material from the Caribbean component of the International Corpus of English and, occasionally, from other digitised text data-bases. Jamaican Creole lexicon and grammar are shown to exert an influence on written English usage, but, generally speaking, direct borrowing of words and rules is much rarer than various forms of indirect and mediated influence, and the over-all impact of the creole is as yet limited. While probably no longer a typical English-speaking society (cf. Shields-Brodber 1997), Jamaica will continue to be an English-using one.