Clinical significance of preoperative serum alphafetoprotein (AFP) levels as a risk indicator of postoperative hepatic metastasis was studied in 74 patients with advanced gastric cancer. The patients consisted of 8 showing more than 20 ng/ml of serum AFP (high AFP cases) and 66 showing less than 20 ng/ml (low AFP cases). Four (50%) of the 8 high AFP cases and 5 (7.6%) of the 66 low AFP cases had already hepatic metastasis before operation. Curative operation was performed in 4 out of the 8 high AFP cases, and hepatic metastasis was observed in 3 (75%) of the 4 cases 3 to 8 months (mean; 6.3 months) after operation. In 49 low AFP cases undergoing curative operation, 5 (10.2%) showed hepatic metastasis 4 to 27 months (mean: 19.2 months) after operation. These results indicate that a risk of postoperative hepatic metastasis is significantly high (p<0.01) in high AFP cases, and hepatic metastasis occurs in a significantly shorter period (p<0.05) after surgery in the same cases. Immunochemical studies suggest a possible difference in the mechanisms of hepatic metastasis between high AFP and low AFP groups.