This paper examines the neurobiology of fluid cognitive functions of the prefrontal cortex and considers learning disability as a specific example of a group of developmental disorders characterized by fluid skills impairment in the presence of crystallized intelligence in the normal range. Research indicating fluid cognitive impairments in children with learning disability is reviewed and developmental and measurement implications of these findings are discussed. It is concluded that advances in knowledge of the neurobiology of the prefrontal cortex and in the measurement of fluid cognitive functions can play a central role in progress in learning disabilities research.