P28/PSMD10, a regulatory complex of the human 26S proteasome, plays a critical role in tumor genesis. This study was designed to clarify the clinical significance of p28GANK in gastric cancer. In order to demonstrate the importance of p28GANK expression for the prognosis of gastric cancer, p28GANK expression in 124 paired cases of gastric cancer and noncancerous regions and immortal gastric epithelial cell GES-1 and 5 human gastric cancer cell lines was analyzed by RT-PCR in real-time. MTT was used to observe the effect of P28GANK on cell growth. p28GANK expression was higher in gastric cancer tissues than in corresponding normal tissues (p = 0.0033), and patients comprising the group with p28GANK high expression had a poorer overall survival rate than those from the low expression group (p = 0.0037). Further, the results of multivariate analysis demonstrated that the high p28GANK expression was an independent prognostic factor of gastric cancer process. p28GANK expression was also up-regulated in five gastric cancer cell lines. As it has been shown by in vitro proliferation assay, p28GANK expression correlated with tumor growth. On the base results of present study one can suggest the p28GANK being useful as a predictive marker for patient prognosis and a novel therapeutic target for gastric cancer.