Abstract: Levels of serum gastrin (GAS) were measured in 42 patients with colorectal cancer and 28 patients with colorectal adenoma in radioimmunoassay (RIA), at times of preoperations, postoperatiQns and more than half a year after operations. Extracts from 8cancers and their adjacent tissues and tissues scm from cancers were examined. The results showed: hypergastrineamia was found in patients with coloretal neoplasia. Serum gastrin levels in the cancer group (192. 41 103. IPg/ml) were higher than those in the adenoma group (134. 95 1 103. 95 Pg/ml,PMO. 05),and much higher than those in the control group (77. 14I39. gpg/ml,P0' 01), and levels in adenoma group were higher than those in control group either (P0. 05). After excision of cancers and adenomas,the levels of serum gastrin were reduced nearly to the levels of control group, but re-elevated nearly to their preoperative levesl after more than half a year. Gastrin contents in cancers (10. 7 1 4. gpg/g) were significantly higher than those in tissues scm far from cancers (4. 4f0. SPg/g), but were not different from those in the adjacent tissues (8. 2± 3. 6Pg/g). This suggests that the expressions of gastrin were enhanced in tumor cells and this may be the exact cause of hypergastrineamia. Serum gastrin monitoring may have benificial diagnostic and prognostic values in patients with colorectal neoplasia, and tumor excisions must be made more than scm far from masses. The author also discussed the possible application of anti--gastrin therepy in patients with colorectal neoplasia.