Background: The human gastroduodenal pathogen, Helicobacter pylori, is characterized by an unusual extent of genetic heterogeneity. This dictates differences in the antigenic pattern of strains resulting in heterogeneous human humoral immune responses. Here, we examined the antigenic variability among a group of 10 strains isolated from Portuguese patients differing in age, gender, and H. pylori-associated gastric diseases. Material and Methods: Immunoassays were performed on two-dimensional electrophoresis gels obtained for the proteome of each strain, using a commercial pool of antibodies produced in rabbit, against the whole cell lysate of an Australian H. pylori strain. Relevant proteins were identified by mass spectrometry. Results: Immunoproteomes of the Portuguese strains showed no correlation between the number of antigenic proteins or the antigenic profile, and the disease to which each strain was associated. The Heat shock protein B was the unique immunoreactive protein common to all of them. Additionally, seven proteins were found to be antigenic in at least 80% of strains: enoyl-(acyl-carrier-protein) reductase (NADH); Catalase; Flagellin A; 2 isoforms of alkyl hydroperoxide reductase; succinyl-CoA transferase subunit B; and an unidentified protein. These proteins were present in the proteome of all tested strains, suggesting that differences in their antigenicity are related to antigenic variance. Conclusions: This study showed evidence of the variability of antigenic pattern among H. pylori strains. We believe that this fact contributes to the failure of anti-H. pylori vaccines and the low accuracy of serological tests based on a low number of proteins or antigens of only one strain.