Mixed languages are said to be the result of a process of intertwining (e.g. Bakker & Muysken 1995, Bakker 1997), a regular process in which the grammar of one language is combined with the lexicon of another. However, the outcome of this process differs from language pair to language pair. As far as morphosyntax is concerned, people have discussed these different outcomes and the reasons for them extensively, e.g. Bakker 1997 for Michif, Mous 2003 for Ma'a, Muysken 1997a for Media Lengua and 1997b for Callahuaya. The issue of phonology, however, has not generated a large debate. This paper compares the phonological systems of the mixed languages Media Lengua, Callahuaya, Mednyj Aleut, and Michif. It will be argued that the outcome of the process of intertwining, as far as phonology is concerned, is at least partly determined by the extent to which unmixed phonological domains exist.