One hundred and sixty-eight specimens of precancerous lesions of gastric mucosa were studied with mucohistochemistry,and ABC immunohisto-chemistry stains of MG7 which is a monoclonal antibody against human gastric cancer (GC).In addition,quantitative analysis of cell DNA was performed with flowcytometry in 36 specimens.It was found that the incidence of type I b intestinal metaplasia (IM) was significantly higher in dysplasia and in the mucosa adjacent to GC than in chronic atrophic gastritis (CAG),and the positive rate of MG7-Ag in type Ⅱb IM was significantly higher than that in type Ⅰa,Ⅰb and Ⅱa IM.Type Ⅱb IM could degenerate into dysplasia.MG7-Ag positive rate,DNA aneuploid rate and the percentage of S and G2+ M cells were significantly higher in type Ⅱb IM with dysplasia than in simple type Ⅱb IM.These findings support the supposed progressive course of CAG →type Ⅱb IM→dyspalsia→GC,and type Ⅱb IM with dysplasia is closely associated with GC.