The transfer of labeled albumin from plasma and ascitic fluid to thoracic duct lymph was investigated in seven patients with ascites and portal hypertension. Ascitic fluid albumin gained access to the thoracic duct lymph before it could be detected in the plasma. Plasma albumin appeared in thoracic duct lymph more rapidly than did ascitic fluid albumin. A significantly greater fraction of the thoracic duct albumin was derived from the plasma than from the ascites. It was concluded that while much of the ascitic fluid albumin leaves the peritoneum via the thoracic duct, it contributes far less to the albumin content of thoracic duct lymph than docs plasma.