Blood flow in tumours implanted in TNF−/− and TNFR−/− mice was determined from Hoechst-stained vessels, and was, respectively, 2.5- and 5.3-fold lower than that in tumours in wild-type mice, 3 h following DMXAA at 25 mg kg−1. The gene discussed is TNFRSF1A; the disease is neoplasm.