Summary: Anaesthetised dogs, which had undergone previous splenectomy, were subjected to moderate (30% blood volume) and severe (45% blood volume) hemorrhage. The rate of lymph flow, and of 131I labelled albumin equilibration between plasma and thoracic duct lymph and the thoracic duct lymph albumin concentration were measured before and after hemorrhage. In the moderately bled dogs the rate of lymph flow and the rate of 131I albumin equilibration were unchanged and the concentration of albumin in thoracic duct lymph suggested release of albumin from protein stores immediately after haemorrhage and the release of newly synthesized albumin. In the severely bled animals the rate of lymph flow was increased then drastically reduced. There was no apparent equilibration of 131I albumin between plasma and lymph, nor was there an apparent release of newly synthesized albumin. These findings are suggestive of a gross reduction in the area of the splanchnic nutritive vascular bed after severe haemorrhage.