Once hepatocellular carcinoma (HCC) develops, it repeats intrahepatic metastasis and has multicentric occurrence, which requires frequent treatment. We designed a phase II clinical trail to clarify whether antineoplaston AS2-1, a mixture of sodium salts of phenylacetylglutamine and phenylacetic acid at a ratio of 1:4, prolongs the recurrence-free interval of HCC patients who undergo frequent treatments for recurrence. Ten patients were enrolled in this trial, 2 in stage I, 6 in stage II, 1 in stage III, 1 in stage IV-B at initial diagnosis. Ten patients experienced 35 recurrence-free intervals. Recurrence-free intervals during antineoplaston AS2-1 administration were significantly longer than those without antineoplaston AS2-1 (16.19+/-15.916 versus 5.05+/-2.897 months: p<0.01). Patients who experienced recurrence-free intervals with and without antineoplaston AS2-1 showed longer intervals during antineoplaston AS2-1 administration than those before and after antineoplaston AS2-1 administration (14.47+/-13.821 versus 5.07+/-2.989 versus 5.02+/-3.009 months: p<0.05). Two patients in stage I showed longer recurrence-free intervals than those in more advanced stages. In conclusion, antineoplaston AS2-1 could not prevent recurrence of HCC but prolonged the recurrence-free interval between regional treatments and improved survival rate of these patients.