In this study the effect of K-76, a sesquiterpene compound with anticomplementary activity isolated from a fungus culture, on carrageenan-induced colitis was studied from biochemical, histological and immunohistopathological aspects. K-76 suppressed epithelial cell loss, crypt abscess formation, inflammatory cell infiltration, mucosal atrophy, and ulceration. Immunohistochemical examination of the colonic mucosa showed that the number of IgG- and IgM-positive plasma cells and the staining intensity for IgG and C3 were increased in carrageenan-induced colitis, but these changes were inhibited by K-76. Besides, serum mucoprotein concentrations and CH50 levels were lower in the animals treated with carrageenan alone. K-76 exerted multifunctional activity, although its mechanisms of action remain obscure.