Recently, an increased frequency of thromboembolic events has been reported after the administration of anticancer drugs. The precise mechanism by which these vascular phenomena occur is unknown. The current work aims at evaluating the alterations of the coagulation and the fibrinolysis systems during the administration of antineoplastic agents by means of newly developed markers of haemostasis. This investigation comprised 25 lung cancer patients treated with multidrug combination chemotherapy. D-dimer, plasmin-alpha 2-antiplasmin complex, fibrin degradation products, fibrinogen, antithrombin III, thrombin-antithrombin III complex, prothrombin time and activated partial thromboplastin time were measured from samples taken before and on days 2, 5, 7, 14 and 21 after the administration of antineoplastic drugs. A significant reduction in plasma concentration of fibrinolytic activity markers, DD and PAP, was observed on days 5 and 7, and on days 2, 5, 7 and 14, respectively, following the administration of chemotherapeutic drugs. Statistically significant shortening of PT and APTT on days 2, 5, 7 and 14, as well as significant elevation of the thrombin generation marker TAT were observed on days 5 and 7 after chemotherapy. These results show that relatively higher levels of coagulation activation and a lower fibrinolytic activity occur during cytotoxic drug therapy compared with basal values. Small variations of haemostatic values and a short follow-up period may explain why no thrombotic events were observed during this study. Although further studies must be done to clarify these findings, the results of this investigation suggest that an imbalance of the coagulation-fibrinolysis system might be a contributing factor in the pathogenesis of thrombotic complications during chemotherapy.