Experiments were performed in anesthetized Macaca fascicularis monkeys to examine the renal hemodynamic responses of these animals to a 15% blood volume expansion using isooncotic dextran in isotonic saline. 20 min following the onset of volume expansion, effective renal plasma flow had increased 80%, glomerular filtration rate was unchanged from control and filtration fraction had decreased 34%. At 50 min, effective renal plasma flow was still increased 74%, glomerular filtration rate had increased 39% and filtration fraction remained decreased 24%. These disproportionate changes in renal plasma flow and glomerular filtration rate are similar to the reported effects in man. Furthermore, they would suggest that glomerular filtration in the primate may not be highly plasma flow dependent under these conditions.