Of the common responses elicited by differences in the composition of the meal, specific effects on renal fluid-electrolyte excretion that manifest themselves as postprandial natriuresis have attracted significant interest. Unfortunately, our understanding of their mechanisms remains incomplete. Hepatorenal reflexes, dopamin action, urodilatin secretion and NO synthesis have been the candidates most frequently cited to contribute to postprandial natriuresis. The recent identification of a novel class of natriuretic peptides named guanylins has brought a new impact on water-sodium homeostasis regulation studies. The elucidation of mechanisms of postprandial natriuresis can be of importance in the research of primary hypertension. The article briefly reviews work in this area.