Administration of the antioxidants 2(3)-tert-butyl-4-hydroxyanisole (BHA) or 5-(P-methoxyphenyl)-3H-1,2-dithiol-3-thione (ADT) to female CD-1 mice starting 4 weeks after infection with 70 cercariae of Schistosoma mansoni resulted in a decrease in the size of the inner fibrotic region of the hepatic granuloma. The cellular composition of the granuloma was not altered by treatment with these two compounds. The administration of the specific superoxide scavenger copper diisopropylsalicylate (CuDIPS) resulted in a similar decrease in granuloma size, suggesting a role of superoxide radicals in the granulomatous response.