This article reviews selectively the literature on the effects of breakfast on cognition and school performance. The focus is on studies published in refereed journals after 1978 that tested those effects on well-nourished and nutritionally at-risk children. In at-risk subjects (defined by clinical history and anthropometry), a morning and overnight fast had adverse effects on cognition, particularly the speed of information retrieval in working memory. Contradictions in the data from different studies prevent definitive conclusions on whether well-nourished children experience similar functional deficits. Nonetheless, available information suggests that brain function is sensitive to short-term variations in the availability of nutrient supplies. Moreover, well-conducted evaluations suggest that the availability of feeding programs in public schools throughout the academic year increases the probability that children will eat breakfast and improve their educational status. J Am Diet Assoc. 1995; 95: 1134-1139.