This study investigated: (1) the relationship between the development of information processing capacity and certain Piagetian logical reasoning abilities; and (2) how the development of these cognitive abilities related to acquisition of certain measurement concepts. Forty first-grade children were individually administered tests of conservation of length and number, transitivity of length, information processing capacity, and basic length measurement concepts. The Piagetian measures of logical reasoning were positively correlated with information processing capacity, but the measures of information processing capacity failed to account for much of the variability of performance on the logical reasoning tasks. Some children at the highest levels of processing capacity failed the logical reasoning tasks and some at the lowest level passed them, suggesting that the logical reasoning tasks are not simply measures of information processing capacity. Furthermore, information processing measures accounted for 25% of the variance in performance on the linear measurement tasks, and length conservation accounted for an additional 23%. Although these two measures accounted for almost half of the variance, it is not clear that they represent prerequisites for learning basic length measurement concepts. Some children at low levels on both measures successfully completed the measurement tasks. (Author/MNS)