Recent work suggests that the apparent shift from thematic to taxonomic concept organization reflects changes in children's preference for these forms of organization, rather than their capacity. A study was made to assess toddlers' knowledge of the different possible relations for the same concept and to extend the triad method to children under three years of age by employing an elicited imitation technique. Attempts were made to elicit both thematic and similarity relations for several target concepts. Forty-one subjects, assigned to younger and older toddler age groups with mean ages of 21 and 33 months, were given an imitation conceptual preference task involving triads of objects. On each trial, the experimenter modeled and described a similarity relation between the target and a second object, and a thematic relationship between the target and a third object. No differences were found between the groups' imitations of either type of relationship alone. However, older subjects were more likely than the younger subjects to imitate both relationships, and less likely to produce partial or incorrect responses. The results indicate an increase with age not in the availability of similarity and thematic relations, but rather, in the flexibility with which both relations will be produced. (Author/RH)