The purpose of this study was to longitudinally examine the development of symbolic play in 2-year-old Japanese infants. The subjects were four children who were individually tested once a month from the age of 12 to 24 months in laboratory settings. Assessment materials consisted of three sets of miniature toys, a doll and junk objects. Each set was presented to each subject for 5 minutes and the subject's spontaneous behavior was individually observed and tested by a female experimenter in the presence of his/her mother. Results indicated that although the developmental sequence of symbolic play was almost always the same, the developmental pace varied among the subjects. Symbolic manipulative play was preceded by the relational play. Non-relational manipulative play was dominant in general. Symbolic play went through a transition from imitative use to substitution and then to the gestural representation of absent objects, and a shift in agent use from self to passive other and then to active other. However, most symbolic play fell in the category of imitative use of self agent use. The mother, in contrast to the experimenter, was always the first passive other agent. Results further suggest a positive relationship of symbolic play to language development. As general indices for all stages in the development of symbolic play, the number of different acts was suggested to be more appropriate than the percentage of occurrence. Developmental characteristics of relational developmental play and egocentricism are discussed. (Author/RH)