BACKGROUND/AIMS: Active hexose correlated compound (AHCC) is a newly developed functional food. In vitro experiments have shown that AHCC enhances natural killer cell activity, and may be considered a potent biological response modifier in the treatment of cancer patients. However, the effects of AHCC in a clinical setting have not been reported. We seek to determine whether AHCC can improve the prognosis of hepatocellular carcinoma (HCC) patients following surgical treatment. METHODS: A prospective cohort study was performed from February 1, 1992 to December 31, 2001. A total of 269 consecutive patients with histologically confirmed HCC were studied. All of the patients underwent resection of a liver tumor. Time to treatment failure (disease recurrence or death) and ten parameters related to liver function after surgery were examined. RESULTS: Of the 269 patients, 113 received AHCC orally after undergoing curative surgery (AHCC group). The AHCC group had a significantly longer no recurrence period (hazard ratio (HR), 0.639; 95% confidence interval (CI), 0.429-0.952; P=0.0277) and an increased overall survival rate (HR, 0.421; 95% CI, 0.253-0.701; P=0.0009) when compared to the control group by Cox's multivariate analysis. CONCLUSIONS: This study suggests that AHCC intake can improve the prognosis of postoperative HCC patients.