This study was performed in order to assess the relative role of cholestasis in increasing some serum glycoproteic markers of malignancy (CA 19-9, TPA, CEA). 30 Patients with benign and 16 with malignant extra-hepatic cholestasis were studied on admission (stage A) and after the operative or spontaneous resolution of the cholestatic picture (stage B). CA 19-9 and TPA were found to be lower in stage B than in stage A benign diseases. A similar behaviour was found in malignant diseases, although findings were significant only for CA 19-9. In neither of the patient groups was CEA found to present a significant trend. Extra-hepatic cholestasis appears able to increase per se serum glycoproteic markers in benign diseases, with variations proportional to the severity of the clinical picture. The same considerations can apply to malignancies, even if in these situations the production of tumour markers by the neoplastic growth should also be considered. We should therefore be cautious in assessing the diagnostic usefulness of new tumour markers when cholestasis is present.