We monitored the antitumoral and antimetastatic effects of tiazofurin (2-beta-Dribofuranosylthiazole-4-carboxamide, TR) on human (HWT) and rat (RWT) Wilms' tumor grafts transplanted orthotopically underneath the renal capsule of scid mice and in rat Wilms' tumour, immunocompetent F344 rats. Treatment with different doses of Tiazofurin, twice a week proved therapeutically effective, since they resulted in a significant decrease in inhibition of both human and rat nephroblastoma grafts. We also applied combined surgical and chemotherapeutic treatment using orthotopic rat Wilms' tumor. The primary tumor was removed 13 days after tumor implantation. TR treatment was started immediately after the implantation of the isograft or following surgical removal of the primary tumor and chemotherapy was followed for 13 days. A high cure rate was found from combined treatment compared to surgery alone. TR treatment resulted in a significant inhibition of the growth of the primary tumor. TR decreased also the frequency and size of recurrent tumors, and appeared to exert selective antimetastatic effects, unrelated to cytotoxicity toward tumor cells. Our results indicate that TR may be a potential alternative chemotherapeutic in the treatment of human Wilms' tumor.