The hypothesis tested was that enteric parasites that induce local inflammation in their host suppress inflammatory reactions at distant sites. A technique was developed to demonstrate, quantitatively, such an anti-inflammatory component. The systemic antiphlogistic effect produced by the intestinal stages of Trichinella spiralis was studied and compared with that caused by dexamethasone, a synthetic adrenocortical steroid. Inflammation was measured (dry weight, protein content, myeloperoxidase activity) as the amount of granulation tissue accumulated around a sterile cotton string implanted for 1 wk under the abdominal skin of rats. Based on this assay, T. spiralis infection had a systemic anti-inflammatory effect on the host which was directly dose related. Steroid treatment also had a dose-dependent suppressive effect on granuloma formation. The maximum dose (56 X 10(3) larvae/kg body weight) of T. spiralis used, had suppressive activity equivalent to 1.0 mg/kg body weight of steroid.