Using sections of formalin-fixed, paraffin-embedded tissues from 64 colorectal cancer patients, the expression of c-erbB-2 oncoprotein was studied immunohistochemically. Twenty-seven percent of the cases with liver metastasis showed positive staining. On the other hand, only 3% of cases without liver metastasis were positive. Expression rates of c-erbB-2 protein in liver metastasis cases showed no significant difference between primary operation (26%) and recurrence (27%). Of all c-erbB-2 positive patients, 90% (9/10) had liver metastasis. Secondly, vessel invasions of 45 rectal cancer patients were studied using Victoria Blue (VB) elastic staining and endothelial staining by factor VIII-related antigen and Ulex europaeus agglutinin I (UEA-I) lectin. VB-HE double stain was efficacious to detect vascular invasion, but endothelial staining was not. There were statistically more vascular invasions in 30 patients with liver or lymph node metastases than in those without metastasis. And in cases with metastasis, many vascular invasions into the extra-muscular layer were seen. Both vascular invasions and c-erbB-2 protein were valuable indicators of possible liver metastasis.