A GROUP MEASUREMENT INSTRUMENT WAS CONSTRUCTED TO TEST THE DEVELOPMENT OF CRITICAL THINKING IN YOUNG CHILDREN. DESIGNED TO ELICIT CHOICES OF THE MOST SATISFACTORY OF 3 ALTERNATIVE CONCLUSIONS FOR EACH OF 26 INCOMPLETE STORIES PRESENTED IN CARTOON PANEL FORMAT, THE INSTRUMENT MEASURES THE DEVELOPMENT OF THE 4 PIAGETIAN CONCEPTS OF CONSERVATION, CAUSALITY, RELATIONS, AND LOGIC. THE TEST WAS INITIALLY ADMINISTERED TO 1,972 CHILDREN IN THE BOULDER (COLORADO) SCHOOL DISTRICT. HOMOGENEITY RATIOS, RELIABILITY COEFFICIENTS, AND INTERITEM CONSISTENCIES WERE COMPUTED FOR EACH OF THE CONCEPTUAL SCALES. THE LOGIC AND RELATIONS SCALES APPEARED TO CONTAIN ITEMS WHICH WERE TOO DISSIMILAR AND, AS A RESULT, FAILED TO CLUSTER SATISFACTORILY. THE CONSERVATION AND CAUSALITY SCALES, HOWEVER, EXHIBITED STATISTICALLY SIGNIFICANT INTERITEM CONSISTENCIES. MEAN SCORES ON THE CONSERVATION AND CAUSALITY SCALES WERE COMPUTED AS A FUNCTION OF CHRONOLOGICAL AGE, AND AGE-RELATED TRENDS WERE FOUND TO EXIST IN THESE AREAS. THE RESULTS THUS FAR SUGGEST THAT THIS GROUP MEASUREMENT INSTRUMENT IS A PROMISING MEANS FOR OBTAINING INFORMATION WHICH HAS HERETOFORE BEEN OBTAINED ONLY IN CLINICAL TESTING WHICH INVOLVES THE EXTENSIVE INTERVIEWING OF EACH SUBJECT. THIS PAPER WAS PRESENTED AT THE 1967 ANNUAL CONVENTION OF THE NATIONAL SCIENCE TEACHERS ASSOCIATION. (JS)