Objective: Identification of serum Pepsinogen I levels in gastric cancer. Materials and Methods: Serum pepsinogen I levels was measured by enzym-linked immunosorbent assay (ELISA) on 32 patients in the gastric cancer group diagnosed by endoscopy and histology and control group of 30 patients with functional dyspepsia on endoscopy Using the cut-off value: PGI ≤ 70 ng / ml for gastric cancer.