Abstract: Objective 　To detect the amplification and protein expression of gene mdm2 in cardia gastric carcinoma and investigate their pathological clinical value. Methods 　Gene amplifications were detected by differential Polymerase Chain Reaction (dPCR) and protein expressions were screened by flow cytometry (FCM) and immunohistochemist ry ( IHC) . Results 　Mdm2 amplifications were found in 7 of 38 case (18. 42 %) . The values ( FI) of mdm2 expression detected by FCM were 1. 45 ±0. 34 and 1. 00 ±0. 13 in cardia gastric carcinoma and normal cardia gastric mucosa respectively ( P < 0. 01) . The positive rate of immunohistochemical staining for mdm2 protein were 64. 86 % and 0. 00 % in cardia gastric carcinoma and normal cardia gast ric mucosa respectively ( P < 0. 01) . Positive cases of mdm2 gene amplification and expression in higher grade group was higher than that in the lower grade group (33. 30 % VS 5. 00 %, 80. 00 % VS 47. 06 %, P < 0. 05) . Conclusion 　Mdm2 gene amplification and expression play an active role in cardia gast ric oncogenesis. The detection of these alternations may be helpful to assess the prognosis of cardia gastric carcinoma.