Soluble forms of ICAM-1 (sICAM-1) and VCAM-1 (sVCAM-1) have been reported from the supernatant of cytokine-activated endothelial cells, cancer cells and from sera of cancer patients. We measured sICAM-1 and sVCAM-1 from the serum of 20 healthy volunteers and 142 gastric cancer patients by ELISA assay. Ninety-five patients were operable and 47 patients were in-operable at the time of this study. Particularly in the 28 operable patients, we sampled both portal and peripheral blood simultaneously and measured the levels of the soluble forms of cell adhesion molecules (sCAMs). The sCAMs level and sero-positivity rate increased with cancer progression in order of the healthy controls, operable patients, and inoperable patients. In in-operable cancer, the sICAM-1 level increased more with liver metastasis. sICAM-1 and sVCAM-1 did not correlate with each other in either portal or peripheral blood. A total of 58.3% of patients with liver metastasis and 22.9% of patients without liver metastasis showed synchronous expression of both sCAMs (p = 0.03). Synchronous sero-positivity of sCAMs and alpha FP was higher with liver metastasis (p = 0.01). The median overall survival duration which co-expressed both sCAMs was 9 months. This showed a significant difference compared with the sICAMs non-expressing group, where the median survival was not reached until 24 months follow-up (p = 0.002). The synchronous expression of sCAMs was an independent risk factor in gastric cancer patients. We raise the possibility that synchronous sICAM-1 and sVCAM-1 elevation may be a useful monitor to determine tumor burden in gastric cancer.