The paper investigates a sample of ‘backchannels’, a kind of response item, in the Cobuild Corpus. Its object is to chart the occurrence of backchannels in modern English speech, and especially to find out if they can indicate how much of a language sequence is needed for a listener to understand the intended message. The sequences into which backchannels are inserted and their insertion points are therefore classified, and the fairly numerous sequences where backchannels “interrupt” a linguistic unit are singled out for special study. A general conclusion is that in the cases where there is no explicit information about the part of the message following the inserted backchannel, the message will nevertheless mostly be understood even at the backchannel insertion point. A comparison between male and female speakers shows that women use backchannels more than men and that, unlike men, they prefer unemphatic backchannels.