The general objective of this study was to study Piaget's notion of the sequential development of number conservation in 85 children averaging 5.9 years of age. The question addressed was to determine if a set of ten equal addition conservation of number tasks were scalable. A large coefficient of reproducibility, .912, was computed. Other indices computed suggest that the obtained coefficient was not artifactual. This study appears to validate Piaget's contention that cognitive development is sequential, suggesting that conservation of number on equal addition tasks may be a single attribute of a whole scalable universe of conservation. (Author)