Glucose administration regulates many neural and behavioral processes in rodents, including learning and memory. Given the important role of glucose in brain function and the safety of glucose as a treatment, we have investigated the effects of glucose administration in humans of different ages. In previous work, we examined the effects of early-morning glucose consumption on cognitive functions in elderly individuals. In this population, glucose enhanced performance on specific measures, particularly on those tasks where mild age-related deficits appear (e.g., verbal declarative memory). Interestingly, glucose failed to enhance cognitive functions in young adults. Our recent work has examined three issues related to glucose enhancement of cognition: First, is glucose effective only in reversing impairments or can it also facilitate performance in highly functioning individuals? Second, are glucose effects dependent either on time of day or on interactions with other meals? Third, are typical breakfast foods as effective as glucose in enhancing cognitive performance? Our findings suggest that glucose can improve memory in highly functioning populations as it does in populations with deficits. However, enhancement by glucose may require sufficient levels of task difficulty and of blood glucose. In addition, like glucose, early morning consumption of cereal can improve performance on some cognitive tests. These results have important implications for the nature of glucose facilitation of memory and for the role of dietary factors in performance of many daily activities.