Background: Perceptual ratings provide a means of evaluating conversations involving individuals with aphasia. The influence of sampling segments of conversation and of segment length has not been established. Aims: To investigate the impact of the duration of the conversational segment on judges' perceptual ratings of elements of conversations between individuals with aphasia and their conversation partners. Methods & Procedures: A total of 64 speech pathology student judges rated two previously video-recorded conversations, elicited through a video-retelling tasks, between two individuals with severe aphasia and their respective partners via the Meas- ure of Skill in Supported Conversation and the Measure of Participation in Supported Conversation (Kagan et al., 2004). Each judge was randomly assigned a segment from one or both conversations. The segment lengths were 3 minutes, 5 minutes, 10 minutes (for the longer conversation only), and the entire conversation (10:30 minutes and 19:17 minutes). The effect of segment duration and the interaction between conversation and segment duration were analysed for each rating scale using a 2 × 3 factorial analysis of variance. Outcomes & Results: There was no significant main effect for segment duration for any of the four rating scales of the Measure of Skill in Supported Conversation and the Measure of Participation in Supported Conversation. Conclusions: Aphasiologists who utilise these ratings of conversation as outcome measures can base the ratings on a segment of the conversation rather than the entire conversation. A 3- or 5-minute segment of a longer conversation on which no time limit has been placed is adequate to provide an accurate perceptual judgement.