AbstractRoper Kriol exhibits variation in the shape of the first-person singular pronoun in subject position. This paper provides an account of the numerous syntactic, semantic and pragmatic factors that appear to influence the selection of eitheraiormibased predominantly on a study of a corpus of the written language. It is claimed that the synchronic distribution ofaiandmiis an innovation primarily motivated by speaker reanalysis of the semantic entailments frequently associated with English subject and object arguments – effectively evidence of the partial grammaticalisation of agentivity in these varieties. This work has implications for our understanding of ‘agentivity’ as a cross-linguistic, cognitive category and for the dynamic relationship between semantic roles and the morphosyntactic encoding of grammatical relations.