Objectives: To determine cagA, vacA virulence factors of Helicobacter pylori in gastric cancer. Materials and Methods: The subjects consisted of 127 gastric cancer patients diagnosed by endoscopic observation and confirmed by histopathological examination from biopsy specimen. This is a crossing described prospective study and the data were analyze by SPSS 20.0 software. Results: A total of 127 gastric cancer patients were recruited, comprising of 98 males, 29 females (males/females rario: 3,4) aged from 34-87 years old, mean 63,2years. All patients were diagnosed as advandced gastric cancers, the location of antral and antral incisura angularis of lesser curvature tumors were 50,6 percent. Gastric differentiated adenocarcinoma was 85,1 percent (moderately differentiated adenocarcinoma was 52,8 percent)
and signet ring cell carcinoma was 7,9 percent. The overall prevalence of H. pylori infection was 54,3 percent. Thirty eight H. pylori strains were obtained by culture. cagA gene was found in 100 percent of the isolated strains in which East Asian-type icagA was 94,7 percent and Western-type cagA was 5,3 percent.. About 300 bp region located upstream of the first cagA EPIYA motif, all strains carrying East Asian-type cagA had 18 bp (84,2 percent, 32/38) or 39 bp (10,5 percent, 4/38) deletion. No strains carrying Western-type cagA had these kinds of deletion. vacA sl genotype was found in all strains. The vacA ml and m2 genotype were found in 60,5 percent. and 39,5 percent. East Asian-type cagA strains were vacA sl/ml (60,5 percent, 23/38), East Asian-type cagA and Western-type cagA strains were vacA sl/m2 (34,2 percent, 15/38), (5,3 percent, 2/38), no strains carrying s2/ml or s2m2 were found. Conclusions: the study found that the prevalence of Helicobacter pylori injection in gastric cancer patients in Vietnam was 54,3 percent. The ratio of cagA(+) was 100 percent, East-Asian type cagA (94,7 percent), Western type cagA (5,3 percent) and the ratio of cagA sl was 100 percent, vacA sl/ml( 60,5 percent), vacA sl/m2 (39,5 percent). The 18-bp deletion type cagA was 84,2 percent (32/38), this is a characteristics of H. pylori strains isolated from Vietnam.