Helicobacter pylori is a spiral-shaped Gram-negative bacterium. It colonizes the gastric mucosa of humans and persists for decades if not treated. Helicobacter pylori infection affects more than half of the world's population and invariably results in chronic gastritis. The cagA gene is present in about 60 to 70% of H. pylori strains; it encodes a high-molecular-weight protein (120 to 140 kDa) and several investigators have noted a correlation between strains that possess cagA and the severity of gastric mucosal inflammation. We examined the relation between cagA status in H. pylori strains and chronic gastritis with inflammatory processes in children from Marília, São Paulo, Brazil. One-hundred-twenty-one children were analyzed histopathologically and by polymerase chain reaction (PCR) to detect H. pylori and cagA. We then looked for an association between cagA presence and inflammatory infiltration. Using histology and PCR, we found 47% H. pylori positive infection; 29 children were diagnosed with chronic gastritis, while 28 showed normal mucosa by histopathological analysis. CagA presence was genotyped in both groups, and an inflammatory infiltrate was studied in all infected children with chronic gastritis. We found cagA strains in 20 of 29 (69%) children with chronic gastritis and 18 of 28 (64%) with normal mucosa, demonstrating a strong relationship between the strains and the inflammatory process. We found a positive association between an inflammatory process associated with H. pylori of cagA+ strains and chronic gastritis development.