The paper focuses on <i>and</i>-parenthetical clauses. It opens with a discussion on their typical places of interpolation and recognises two major types: a) anchored parentheticals and b) floating parentheticals. The <i>and</i>-clauses are then contrasted to coordination proper. The syntactic relation of the parenthetical with the host is examined in the context of the integrated and the unintegrated approaches, but only to demonstrate that none of them is satisfactory. Instead, I refer to the <i>Insertion </i>theory of Ackema and Neeleman (2004) to accommodate <i>and</i>parentheticals. Finally, this paper analyses the speaker’s motivation behind using such cumbersome interruptions and I conclude that it is in line with his aim at optimal relevance. The examples presented in this study are collected from two English corpora.