Serum pepsinogens Ⅰ and Ⅱ (PGI, PG Ⅱ) levels were determined by PGI and PG Ⅱ-RIA kits in 84 healthy controls and 128 patients of gastric diseases including 42 patients with gastric cancer. The results showed peptic ulcer cases had elevated PG I and PG Ⅱ levels. The atrophic gastritis cases had low PGI levels and the gastric cancer cases had low PGI and low PGI/PG Ⅱ ratio. Using the cut-off values of PGI<35µg/L and PGI/PG Ⅱ<1.5 for clinical purpose, the sensitivity and specificity of the test for gastric cancer was 73% and 78%, respectively. Combined with endoscope examination, the serum PGI and PG Ⅱ levels are valuable for the early diagnosis of gastric cancer.