The purposes of this study were to: (1) determine the influence of a series of experiences involving the equivalence relation "same length as" and the asymmetric transitive relations "longer than" and "shorter than" on the ability of first and second grade children to classify and seriate objects on the basis of length; (2) investigate the influence of such experiences on the child's ability to conserve and use the transitive properties of the length relations; (3) determine if the subject's ability to use the transitive property of the equivalence relation "same length as" was related to his ability to classify on the basis of the relations; (4) investigate the relationship between the child's ability to use the transitive property of the relations "longer than" and "shorter than" and his ability to seriate on the basis of these relations; and (5) determine if the ability to seriate linear objects is material specific or relation specific. The subjects were 39 first grade and 42 second grade children. Two instructional units were written and taught to acquaint the students with relations used in the study. Tests administered were: Criterion Test, Conservation of Length Relations Test, Transitivity of Length Relations Test, Seriation Test, and Classification Test. The results clearly confirm the hypothesis that seriation ability of "linear" objects can be improved by training. (DB)