Niridazole is a potent inhibitor of certain expressions of delayed-type hypersensitivity; however, its effect and specificity on other immunologically induced mononuclear cell infiltrates has not been determined. We therefore tested this drug in a model of auto-antibody-induced renal tubulointerstitial disease (RTD), which is characterized by the accumulation of lymphocytes and macrophages in the cortical interstitium. Niridazole-treated (100 mg/kg) and untreated guineapigs were injected with potent anti-tubular basement membrane serum from donors with RTD. Drug treatment was repeated 2-3 times during the course of 10 days. The characteristic renal lesions were found in both groups. However, a single dose of niridazole inhibited skin reactivity in tuberculin sensitive guinea-pigs for at least 8 days. These findings further support the contention that immunologic tissue injury in RTD does not involve mechanisms of delayed-type hypersensitivity.