To investigate the relationship between the concentration of interleukin-1α (IL-1α) and liver metastasis in gastric cancer, the concentration of IL-1α was measured in homogenized tumor samples from 61 patients with gastric cancer. A significantly higher concentration of IL-1α was observed in tumors from patients with liver metastasis than in those from patients without liver metastasis; in differentiated type tumors than in undifferentiated type tumors; in tumors associated with moderate to severe venous invasion than in those associated with mild or no invasion; and in tumors with expansive or intermediate growth pattern (INFα, INFβ) than in those with an infiltrative pattern (IFNγ) by Student’st-test. Stepwise logistic regression revealed IL-1α, depth of invasion, venous invasion, and tumor size to be associated independently with liver metastasis. These findings led us to conclude that the IL-1α concentration was on eof the most useful determinants of liver metastasis among the various clinicopathologic characteristics.