Alpha-fetoprotein (AFP) level was measured in five cases of hepatoma before and after hepatic lobectomy in order to determine if changes in AFP level were indicative of tumor residual or recurrence. It was felt that if this relationship could be proved, an elevation of AFP level might serve not only as a guide for detecting tumor, but as an indication for reoperation or chemotherapy or both. This study did demonstrate a relationship between the production of AFP and the histological type of hepatoma and its degree of cellular differentiation. The AFP value was also found to be correlated with the size of the tumor.