The effects of a high-protein (HP) and low-protein (LP) meal on glomerular filtration rate (GFR), effective renal plasma flow (ERPF), and renal vascular resistance (RVR) were examined in conscious dogs. Ingestion of the HP and LP meal produced a temporary increase in systemic hemodynamic parameters due in part to a ‘cephalic phase’ of sympathetic excitement. However only the HP significantly altered renal hemodynamics, i.e. GFR, ERPF and RVR. Plasma renin activity (PRA), serum aldosterone and plasma atrial natriuretic peptide (ANP) concentrations were not significantly altered by either a HP or LP meal. Of all the serum electrolytes measured, serum Ca2+ concentrations were significantly lower after a HP meal. It would appear that protein-meal-induced changes in renal hemodynamics are independent of changes in systemic hemodynamics. The exact mechanism of action of a HP meal on renal hemodynamics is not clear, but it appears that one mechanism by which a HP meal may alter renal hemodynamics is by altered calcium homeosta