Many of H. pylori strains causing gastroduodenal diseases have a cagA gene encoding CagA protein, a virulence factor of these bacteria. Anti-CagA antibodies produced by majority of people infected with CagA(+) strains can indicate such infection. In this study the efficacy of three immunoenzymatic tests: immunoblot (MileniaID Blot H. pylori IgG, DPC Biermann GmbH, Germany) (MB) and ELISA, conducted with a recombinant immunodominant fragment of CagA (rCagA) and full length CagA molecule (flCagA), in detecting CagA(+) and CagA(-) infections, was compared. The 13C urea breath test (13C-UBT) was used for establishing H. pylori status. The serum samples from 157 individuals were used for serodiagnosis. The H. pylori CagA(+) infection was detected in H. pylori infected individuals with similar frequency by MB (64%) and flCagA-ELISA (60%) and little less frequently by rCagA-ELISA (53%). There was a high coincidence between the negative results of these three tests for H. pylori uninfected individuals with no anti-CagA IgG in the serum (96-100%). The results show that rCagA-ELISA and especially flCagA-ELISA are easy, inexpensive and useful noninvasive assays for discrimination of CagA(+) and CagA(-) H. pylori infections in the subjects examined by urea breath test.