There is no established clinical role for the lens culinaris agglutinin-reactive fraction of alpha-fetoprotein (AFP-L3%) and des-gamma-carboxy prothrombin (DCP) in the management of the U.S. hepatocellular carcinoma (HCC) patient population. In order to clarify the clinical usefulness and characteristics of AFP-L3% and DCP, a prospective study was performed on United States patients having histologically proven hepatocellular carcinoma. Ninety-nine histologically proven HCC patients, who were diagnosed with unresectable cancer between July 1999 and March 2001 at the Liver Cancer Center of the University of Pittsburgh Medical Center, were included for analysis. The sensitivity of AFP-L3%, DCP, and AFP was 61.6%, 72.7%, and 67.7%, respectively. The highest sensitivity, 85.9%, was obtained in the combination of three markers. Statistically significant differences were observed for portal vein invasion in AFP-L3% and AFP levels (P = 0.0059 and P = 0.0360, respectively). DCP was significantly associated with metastasis (P = 0.0368). There were significant associations between AFP-L3% and AFP results and patient survival (P = 0.0150 and P = 0.0020, respectively). AFP-L3%, platelet count,and albumin showed a significant difference with respect to outcomes on Cox's proportional hazard model (P = 0.0059, P = 0.0073, and P = 0.0265, respectively). The combination of AFP-L3%, DCP, and AFP was determined to be superior for detection of HCC compared with each marker alone or to other combinations. AFP-L3% was significantly related to portal vein invasion and patient outcomes and appears to be a useful prognostic marker for HCC.