Objective: The purpose of our study was to research the applicability of measuring serum pepsinogen I (PG I) and PG I/pepsinogen II (PG II) ratios as screening tests for atrophic gastritis, which is the most important predisposition for stomach cancer. Materials and Methods:We measured serum pepsinogen levels in non-specifi c gastritis, atrophic gastritis and gastric cancer using a radioimmunoassay method. We included in this study 30 healthy control, 30 nonspecifi c gastritis, 30 atrophic gastritis and 50 gastric cancer cases. Results:The serum PG I level was statistically higher in the control group and in the patient group with chronic nonspecifi c gastritis compared to the patient groups with chronic atrophic gastritis and stomach cancer (p<0.05). The best cutoff values for diagnosing stomach cancer using serum PG I and PG I / PG II ratios were found to be <25 ng/ml for PG I and <3.0 for PG I / PG II. The same cut-off values were also most eff ective for the patients with atrophic gastritis. Conclusions:Serum pepsinogen screening was shown to be a practical predictor of stomach cancer and atrophic gastritis, the most important predisposing lesion for stomach cancer. Although the diagnosis of stomach cancers localized in the pylorus and cardia via this method is diffi cult, we believe that the detection of early-stage cancers that develop following chronic atrophic gastritis in particular will be possible, and therefore the morbidity and mortality of stomach cancer will be decreased.