Almost total obliteration of the peritoneal lymphatic drainage in rats produced no increase in peritoneal fluid. The problem was extended to observe the effect of peritoneal lymphatic obstruction with superimposed infrahepatic portal hypertension on peritoneal fluid dynamics. For controls infrahepatic portal hypertension was produced by partial obstruction of the portal vein with an aluminum clip. In animals with peritoneal lymphatic obliteration and portal hypertension serous fluid accumulation was three times as great as in those with portal hypertension alone and resembled clinical ascites. Such findings indicate that subtotal peritoneal lymphatic obstruction alone does not appreciably affect serous fluid dynamics. However, in the presence of altered physiological mechanisms involved in serous fluid production, obstruction of the lymphatic system may play a significant role in the genesis of ascites.