An attempt was made to develop and validate a Piagetian-based written test with successful use of the logic of specific Piagetian tasks defined as the criterion. Ninety-six randomly selected nine to sixteen year olds, stratified by age, were individually presented the Piagetian tasks of pendulum, balance, and combinations, and group administered a 36-item logically equivalent written test. Restuls indicated that a Piagetian-based written test was successfully constructed. Discussion focused on future lines of research and the possible uses of such a test. (Author)