In this article the author explores aspects of young children's private speech, examining characteristics of their development of discourse knowledge in utterances that are not directed to actual conversants. Two routes are taken, which the author tries to interlink without seeking a hard and fast juncture. The first is a study of what children are doing when they talk into a toy telephone, with reference to a transcript taken from empirical research. Knowledge of the essential structure of telephone discourse is displayed, as are emotional motivations behind the construction of pretence talk. The second is the notion of 'egocentric speech' as coined by Piaget and developed, within his sociocultural perspective to language acquisition, by Vygotsky. The author argues that dominant contemporary presentations of Vygotsky's notion of 'egocentric speech' tend to stress the self-regulatory or planning function at the expense of its role in expression of the imagination. The two discussions come together in the suggestion that the deployment of the imagination in reassembling sociocultural knowledge for the creation of pretence play, sometimes expressed in private speech, can be a significant factor in the exercise of discourse competencies for young children.