The expression of Fas ligand (Fas L) was investigated in sixty-seven patients with colorectal cancer for possible correlation with liver metastasis. Fas L expression was positive in 48 and negative in 19 cases. In Fas L-positive cases, 14 patients had liver metastasis including metachronous metastasis. However, only one case had liver metastasis in Fas L-negative patients (p = 0.0344). In colorectal cancer with venous invasion, 13 from 25 Fas L-positive cases had liver metastasis but only one in 19 negative cases (p = 0.0003). In the cases without venous invasion, no liver metastasis was observed in Fas L-negative cases. These results suggest that Fas L expression may be a predictive factor for liver metastasis in colorectal cancer with venous invasion.