A study was undertaken to determine if a criterion referenced test based on a Piagetian stage model of reading acquisition was related to grade level, to a standardized reading achievement test, and to a test of cognitive developmental level. Sixty first, second, and third grade children were administered a comprehensive test of basic skills. They were then given a Piagetian test of conservation, as well as a criterion referenced test made up of real and nonsense words in a sentence context that was designed to diagnose cognitive developmental reading level. The sentences containing the key words were presented in two alternate forms: one involving a production task (pronouncing the words) and one involving a multiple choice judgment task. The various tests were administered in several sessions, with the order of administration counterbalanced across subjects. The results provided support for a cognitive developmental approach to reading acquisition. The criterion referenced production test based on a cognitive developmental model showed a significant relationship to age-grade level, to a standardized measure of reading achievement, and to cognitive developmental level as indexed by the Piagetian conservation measure. The multiple choice judgment task did not show a significant developmental change. (FL)