This study examined the functions of structured modeling and mother-child play settings upon the development of pretend actions in young Down Syndrome children. Subjects were 30 pairs of Japanese children, with a developmental age range of 12-35 months, and their mothers. The children were individually administered five phases of premodeling, controlled mother-child play, uncontrolled mother-child play, modeling by the experimenter, and post-modeling, in that order. The materials used were lifelike objects, miniature toys, and ambiguous objects. The study's results show that more children increased their levels of pretend actions and showed the highest level of decentration and/or decontextualization in the modeling setting rather than the mother-child play setting. However, modeling produced a decrease in nonmodeled and modified pretend actions with developmental age, while mother-child play showed an increase in the number of different acts. The difference in the two settings was regarded as merely a discrepancy of control, as it was possible to teach the mother to be a more effective model. The study suggests that controlled and uncontrolled settings are appropriate for the acquisition and facilitation of pretend actions in retarded children. An abstract is provided in Japanese. (JDD)