It is well known that a number of antineoplastic agents are able to induce procoagulant cellular activity and tissue factor not only in neoplastic cells but also in normal, monocyte/macrophage cells, and some of them, including adriamycin, even increase procoagulating activity of the factor already expressed, providing a further example of the possible co-participation of chemotherapy in the onset of thrombotic complication in cancer patient. Epirubicin is an analogue of adriamycin but differs strikingly in terms of its collateral effect, in particular being less cardiotoxic. To the authors' knowledge there are no data regarding the possible effect of epirubicin on lympho/monocyte procoagulant activity. This study shows that not only adriamycin but also epirubicin is able to increment the level of lympho/monocyte procoagulant activity "in vitro", with a dose-dependent effect, and to synergize with bacterial endotoxin in increasing this leukocyte activity, although the effect is significantly greater in the case of adriamycin. The importance of these findings at practical and clinical level remains to be defined, in particular in the length of the different pharmacokinetic behavior of these two chemotherapeutic agents and in the context of those neoplastic diseases for which adriamycin and Epirubicin treatment is most frequently used.