This study was aimed at investigating the effect of gastrin on the growth of gastric cancer and evaluating postoperative hypergastrinemia in patients that had received various types of gastrectomy for gastric cancer. RT-PCR for gastrin/CCKB receptor mRNA was performed in human gastric cancer cell lines and tissue. The effect of gastrin or glycine-extended gastrin on the growth of gastric cancer cell lines was determined by MTT assay. Serum gastrin levels were compared with respect to the resection type of gastric cancer surgery. Gastrin/CCKB receptor mRNA expression was detected in all 9 gastric cancer cell lines, and in 19 of 29 (62%) gastric cancer tissue samples. Growth of gastric cancer cell lines containing the gastrin/CCKB receptor was significantly enhanced by gastrin and glycine-extended gastrin. The proximal gastrectomy group had a significantly higher mean serum gastrin level than the distal subtotal gastrectomy, total gastrectomy, or preoperative groups (p<0.05). Our study confirms that a high proportion of gastric cancer tissue samples express the gastrin/CCKB receptor, which can stimulate the growth of gastrin/CCKB receptor-positive gastric cancer cells. In addition, we confirm that hypergastrinemia can be induced in about half of patients after proximal gastrectomy. More studies are needed to clarify the relationship between hypergastrinemia and tumor recurrence after proximal gastrectomy.