1. Simultaneous thoracic duct and hepatic lymph flows were measured in 29 mongrel dogs before and after the intravenous administration of mannitol, ethacrynic acid, frusemide and chlorothiazide in separate experiments.
2. Thoracic duct lymph flow increased significantly after each diuretic agent was administered.
3. Hepatic lymph flow increased only after ethacrynic acid and mannitol administration. Frusemide and chlorothiazide did not alter hepatic lymph flow.
4. These data show that increases in thoracic duct lymph flow after ethacrynic acid and mannitol arise partly from the liver, as well as from other organs.