A study focussing on the notion of 'interlanguage', which has been developed within research on second language acquisition. The author (a) investigates some of the methodological considerations involved in attempting to characterize the notion of 'human interlanguage' in terms of universals; (b) considers the implications of the language-contact situation in attempting to define interlanguages in these terms; and (c) provides examples of logically-possible, but empirically unsubstantiated types of interlanguages which are explained within the framework developed in this analysis.