Research findings in learning disabilities based on Piaget's theory were reviewed. Superimposing the findings of research on Piagetian stages of cognitive development, it appears that during the sensorimotor stage the diagnosis of learning disabilities is difficult. The research findings suggest that there is a delay in cognitive development of learning-disabled children during elementary school years, which corresponds to preoperational, concrete operational, and transition to formal operational stages. From a genetic epistemological perspective, research evidence supports a “developmental lag” approach to learning disabilities. Implications for assessment, curriculum planning, and education are discussed.