Twenty-seven patients treated with high-dose rTNFα, IFNγ and melphalan by isolated limb perfusion were histologically documented. There were 20 cases of melanoma-in-transit metastases and 7 cases of high-grade soft-tissue sarcoma. Biopsies were taken before IFN7, after IFNγ, before TNFα and between 2 hr and 60 days after the TNFα perfusion. Immunohistochemistry was performed for adhesion molecules ICAM-I, ELAM-I (E selectin), VCAM-I and PECAM. During the first hours after beginning perfusion, the endothelial cells of the tumour capillaries appeared swollen. Significant tumour necrosis was already observed 3 hours after the perfusion in melanoma cases. The overall predominant feature was coagulative necrosis associated or not with haemorrhagic necrosis. TNFα induced increased expression of ELAM-I and VCAM-I adhesion molecules on intratumoral endothelial cells. The activated tumour vessels were progressively destroyed. Significant intra-vascular recruitment of polymorphonuclear cells (PMNs) was observed 3 hr after starting TNFα; it was followed by diapedesis and tumour colonization 3 days later. T lymphocytes and macrophages were detected during the first 7 days and B lymphocytes during the second week. Melanoma in transit metastases treated with alkylating agent alone did not show significant necrosis and did not express high levels of adhesion molecules (ELAM-1, VCAM-I) nor infiltration by PMN.