The relationship between free cancer cells and the pathological characteristics of gastric cancer were studied. Of 100 cases of gastric cancer, free cancer cells in the peritoneal cavity were detected in 32 cases (32%). Free cancer cells were most often found in tendonoid (62.2%) and colour diffused (60.0%) serosal types. When the area of serosal invasion was over 20 cm, the positive free cancer cell rate was 56.6% and only 2.5% if below 20 cm. Free cancer cells were related to the depth of cancer infiltration, often found in the S2 and S3 invasion layers, as well as to the pathological characteristics of gastric cancer. Free cancer cells were often seen in infiltrated type cancer, histologically poorly differentiated or undifferentiated adenocarcinoma. and nest or diffused growth types. In patients without peritoneal metastasis (P0), the positive rate was 26.1%. This study proved that Chen’s serosal classification is correct and useful in assessing whether the cancer cells have penetrated through the s