To evaluate a possible association between infection with cag A-positive strains and gastric carcinoma increased risk we studied 119 Helicobacter pylori-positive patients with gastric carcinoma and 119 matched controls. The presence of cag A gene was investigated by PCR in H. pylori isolates and in gastric biopsy specimens. A significant association was found between cag A-positive status and distal gastric carcinoma for both the intestinal and diffuse types of tumor for both males and females. On the other hand, no association was observed between cag A-positive status and proximal gastric carcinoma.