Two experiments were reported investigating the conditions that elicit request-making in the moderately and the severely mentally retarded. In both experiments single-subject designs were used with a store game task designed to closely approximate a naturalistic communication situation. In the first experiment moderately retarded adults were able to consistently communicate which of two objects they wished to obtain from a store counter. In the second, severely retarded adolescents initially made some errors but communicated effectively on 100% of the trials by the end of the experiment. These results contrast markedly with the results from the less naturalistic task used previously. In both experiments the amount of verbalization was greater when the task was arranged to create a demand for communication. Applications of these findings to everyday communicative situations involving the mentally retarded are discussed. © 1983 Pergamon Press Ltd.