The present invention provides methods for detecting Helicobacter pylori (H. pylori) DNA and/or fragments thereof in blood. The first method involves extracting DNA from a blood sample, preferably plasma, by amplifying the DNA using a polymerase chain reaction (PCR) or a ligase chain reaction (LCR) method, and detecting a target DNA sequence in the amplified DNA. The preferred target DNA sequence comprises a Mr26 or a 16S rRNA gene or fragments thereof specific to H. pylori. The second method involves extracting DNA from a blood sample, preferably serum, by hybridizing the extracted DNA with a radioisotope or fluorescence labeled H. pylori DNA probe.