Cognitive performance on "An Inventory of Piaget's Developmental Tasks" (IPDT) was related to the Scholastic Aptitude Tests and performance in both college chemistry lecture and laboratory classes. The IPDT is a valid and reliable 72-item, untimed, multiple-choice paper and pencil inventory with 19 subscales representing different Piagetian tasks. Subjects (N=225) from two different levels of introductory chemistry courses participated in the study. IPDI scores were significantly correlated with SAT's and placement data. Although correlations with course grades were low, "A" students were higher than others in Piagetian development, particularly for the higher level course. Males outperformed females on the IPDT even when course grades were similar. Weakest areas of development as indicated by subscale scores are described with implications for course performance. These student weaknesses are discussed with respect to sex difference as they relate to learning and instructional activities in introductory chemistry classes. (Author/JN)