After plasma containing labeled plasma protein has been given intraperitoneally to dogs with experimental ascites a steady and rather rapid movement takes place of the labeled protein into the circulating blood. When plasma containing labeled plasma protein has been injected intravenously into the ascitic dog the labeled protein steadily disappears from the circulating blood and appears promptly and steadily in the ascitic fluid. The period of complete exchange or turnover in either instance is measured in days (2 to 7), but many factors enter in and make for variation. Lysine labeled with radio carbon is incorporated into the plasma proteins by feeding the donor dog. These experiments emphasize the ready exchange of proteins in the plasma with those in the ascitic pool and vice versa. This exchange may be termed circulation of ascitic protein.