A patient with chronic calcific pericarditis, hepatic congestion, and fibrosis had massive ascites with a protein concentration of 5.1 g/100 ml. This fluid was in all likelihood largely derived from hepatic interstitial fluid. The ascites-serum concentration ratio for several protein species and molecular exclusion chromatography of these fluids suggested two processes may be involved in the transfer of protein from serum to ascites, namely bulk transfer of all species and molecular sieving.