Two groups of children, a pragmatically impaired (PI) group and a group of language-normal (LN) age-matched peers, were compared by use of a referential communication task. Experimenter and child both played the roles of listener and instructor during the task and, in addition, the experimenter sometimes failed to give adequate information when in the role of instructor. Lexical content and structural complexity were controlled, and it was hypothesised that difficulties for the PI group would arise when in the role of instructor, as a result of failing to specify necessary information in order for the experimenter to respond appropriately. In fact, the main difference between the two groups arose when the experimenter failed to give adequate information to the child; the LN children were quick to realise this and to request clarification, whereas the PI children requested clarification to a lesser extent and appeared less aware of the need to do so. Possible explanations for this pattern of results are explored.