Matrix tasks to assess multiple classifications and multiple seriation skills were administered to 160 children (40 Ss each from preschool, kindergarten, first and second grade levels). Each child received six matrix subtasks (reproduction and transportation of cross classification I, double seriation, and cross classification II) in one of six orders of presentation. Preliminary analyses indicated a general absence of significant presentation order effects and an absence of sex differences. Grade level comparisons were significant for all subtasks except cross classification I transposition. Significantly superior performances on the reporduction when compared to the counterpart transposition subtask were shown for the cross classification I (first grade, second grade, and combined grades), double seriation (kindergarten, first grade, second grade, and combined grades), and cross classification II (first grade and combined grades) cases. The between matrix difficulties were that in both reproduction and transposition subtasks, cross classification II was more difficult than double seriation and cross classification I. Results suggested that development in classificatory abilities may lag behind relational abilities contrary to the structural prediction of orthodox Piagetian theory. (Author/SB)