Recombinant tumour necrosis factor-α (rTNFα) possesses the unique property of activating and selectively destroying the tumour-associated microvasculature. Systemic application of rTNFa has shown that the maximum tolerated dose (MTD) is 10 times lower than the efficient dose in animals. The main toxicity corresponds to the systemic inflammatory response syndrome (SIRS), with a decrease of vascular resistance and hypotension. We found that it is possible to administer rTNFa at 10 times the MTD in an isolated limb perfusion system, using a heart-lung machine, for advanced melanoma and sarcoma of the limbs. Our results, using the combination of high dose rTNFa, interferon-γ and melphalan (TIM), produced an overall objective response rate of 1009J- in 2 successive studies on melanoma, with 909r and 78-complete response, respectively. In sarcoma, there was an overall response rate of 64%, with 36rlc complete response. Angiographie and immunohistological studies demonstrated selective and early damage of the tumour-associated microvasculature, preceded by upregula-tion of adhesion molecules and intratumoural leak of von Willebrand factor. Tumour invasion by platelets and, in some cases, by polymorphonuclear cells, appeared within hours after the application of rTNFα, long before the lysis of the tumour. Systemic changes after rTNFoc treatment included the production of soluble TNFα receptors and of interleukin-6. A typical acute phase reaction was observed within 3 days, with increase of C-reactive protein parallelled by an increase of tenascin-C. A selective effect on intratumoural endothelial cells seems to be involved in the mechanism of the impressive antitumour effect of rTNFα, but the role of acute phase protein production is not fully understood. In selected cases of melanoma, specific cytotoxic T lymphocytes were increased after perfusion.