Fifteen patients (8 female, 7 male) with advanced melanoma received intravenous injections of a pyrogenic bacterial lysate consisting of streptococci and serratia marcescens. In three cases with skin metas-tases, this kind of treatment resulted in a total and long lasting remission. In another case with inguinal lymphnode metastases, a five month period of stability was achieved. The remaining eleven patients showed further progression of their disease. Side-effects of therapy included fever, nausea, headache, back pain, and – occasionally – herpes labialis. Laboratory analysis revealed a marked increase in the blood counts of monocytes 24 and 48 hours after injection of the bacterial lysate, while other hemopoietic cells did not show significant alterations. During peak temperatures four to six hours after injection, TNF-alpha serum levels were elevated correlating with the increase in body temperature. The increase in concentration of complexes of thrombin-antithrombin III, prothrombin fragments and soluble fibrin during peak temperatures indicate an activation of the coagulation system without evidence, however, of consumption coagulopathy.