The utility of the markers CEA, beta-HCG, CA-50, alpha-fetoprotein (APF), ferritin, alkaline phosphatase (AP), its isoenzyme liver-1 (APL1), gamma-glutamyltransferase (gGT), its fast migrating isoenzyme (gGT1) and 5'nucleotidase (5'N) in differentiating liver malignancies and benign involvement was evaluated in the sera of 85 patients with hepatocellular carcinoma (HCC), 157 with chronic liver disease (CLD) and 91 with liver metastases (LM) derived from different tumors. The mean concentrations of all the parameters except CEA and GGT1 were significantly different in HCC and CLD, but a broad overlap existed in the two groups, so different cut-offs were considered to assess the positive and negative predictive values and test efficiency (Eff). The best results were observed considering AFP greater than 100 IU/m (Eff0.86), ferritin greater than 800 ng/ml (Eff0.69), CA-50 greater than 100 U/ml (Eff 0.63), beta-HCG greater than 10 mU/ml (Eff 0.61), AP greater than 300 IU/ml (Eff 0.66), the presence of APL1 (Eff 0.78), 5'N greater than 25 mU/ml (Eff 0.70), gGT greater than 100 mIU/ml (Eff 0.63). Among HCC patients 17% did not secrete AFP; in 26% the protein was less than 100 IU/ml and in 36% less than 400 IU/ml. Apart from AFP the most effective marker was APL1. At the above cut-offs more than three parameters were simultaneously positive in 71% of HCC and 9.9% of CLD. CEA, CA50, AFP were the only parameters that distinguished the HCC from the LM group; in the latter, APL1 was also a very sensitive marker (87%) for neoplastic involvement of the liver.