Lymph flow is elevated in most inflammatory conditions. However, a few previous studies have indicated that peritoneal lymph flow may actually fall during acute peritonitis. This study was performed to explore this issue further and to study the pathophysiology of peritoneal exchange during peritonitis. Therefore, we wanted to assess the total peritoneal clearance (Cl) and the clearance from peritoneum to plasma (Cl  P) of ¹²⁵I-labeled albumin (¹²⁵I-albumin) as well as plasma-to-dialysate clearance (Cl  D) of Evans blue-labeled albumin together with peritoneal ultrafiltration (UF) profiles and mass transfer area coefficients of ⁵¹Cr-EDTA and glucose in rats after acute peritonitis induced by zymosan. Zymosan incubation of the peritoneal cavity (120 mg) for 4 h generally led to a 4- to 10-fold increase in peritoneal fluid white blood cell count, indicating that acute peritonitis had been induced. Then 16 ml of 3.86% Dianeal and ¹²⁵I-albumin were instilled intraperitoneally, whereas Evans blue-labeled albumin and ⁵¹Cr-EDTA were given as infusions intravenously. Compared with control, mass transfer area coefficients for glucose and ⁵¹Cr-EDTA increased markedly from 0.43 ± 0.06 and 0.25 ± 0.04 to 0.91 ± 0.06 and 0.59 ± 0.05 (SE) ml/min, respectively, during peritonitis, whereas Cl and Cl  D increased from 32.8 ± 5.6 and 8.6 ± 1.6 to 74.5 ± 7.3 and 12.9 ± 1.0 µl/min, respectively. The UF profile in peritonitis indicated type I loss of UF (resulting from the increases in permeability-surface area product for glucose). However, the Cl  P declined to 5.9 ± 1.0 µl/min from 7.9 ± 0.8 µl/min (P < 0.05) in control. In conclusion, despite marked effects on peritoneal solute transport and on UF, conceivably resulting from vasodilatation and increases in capillary permeability, zymosan-induced peritonitis did not cause any acute increases in direct peritoneal lymphatic absorption.