This paper investigates the intonational phrasing of three types of parenthetical insertions – non-restrictive relative clauses (NRRCs), full sentences, and comment clauses (CCs) – in actual spoken language. It draws on a large set of data from a corpus of spoken British English. Its aim is twofold: first, it evaluates the correctness of previous claims about the intonational phrasing of parentheticals, specifically the assumption that parentheticals are phrased in a separate intonation domain; second, it discusses the implications of the intonational phrasing of parentheticals for prosodic theory. The results of the data analysis are as follows. First, the longer types of interpolations but not CCs are by default phrased separately. Second, both the temporal and the tonal structure of the host may be affected by the parenthetical. Third, CCs lend themselves more readily to the restructuring of intonational phrases such that they are phrased in one domain together with material from the host. Fourth, the prosodic results cannot be explained in syntactic accounts which do not allow for a syntactic relation between parenthetical and host. Fifth, the interface constraints on intonational phrasing apply to parentheticals. Sixth, the intonational phrasing of parentheticals supports the assumption of a post-syntactic, phonological component of the grammar at which restructuring applies.