Numerous studies have suggested a link between iron-deficiency anemia(IDA) and Helicobacter pylori infection. Previously, we found that strains isolated from IDA patients showed higher levels of Fe ion uptake and Fe-iron-dependent rapid proliferation than those of strains derived from patients without IDA. Recently we examined the nucleotide sequences of nap A, fur, and feo B of H. pylori strains from 24 IDA patients and those from 25 non-IDA patients. Frequency of neutrophil-activating protein A(Nap A), which encoded by nap A, with threonine at amino acid residue No. 70 (Thr70-type Nap A) was significantly higher in IDA strains than non-IDA strains. Strains with Thr70-type Nap A showed significantly higher levels of Fe3+ and Fe2+ uptake than strains with other type, Ser70-type Nap A, which is found in standard strains.