In response to the lack of suitable material for assessing idiom comprehension in children with semantic-pragmatic difficulties, a new, play-based methodology is presented. The child listens to a tape-recorded story into which are embedded a range of idiomatic expressions. The child then acts out the story as it is played again, sentence by sentence. The play is video-recorded and transcribed. Actions for each idiom are categorised and are then amenable to within-child, between-child, and between-group analyses. The results of a pilot project indicate that this methodology overcomes may of the problems inherent in assessing children identified as having semantic-pragmatic difficulties.