AIM: To assess the sensitivity and specificity of polymerase chain reaction (PCR) in detecting Helicobacter pylori(H pylori)infection in patients with bleeding peptic ulcers, and to compare its diagnostic efficacy with other invasive and non-invasive tests.METHODS: From April to September 2002, H pylori status in 60 patients who consecutively presented with gastroduodenal ulcer bleeding was examined by rapid urease tests (RUT), histology, culture, PCR, serology and urea breath tests (UBT).RESULTS: The sensitivity of PCR was significantly higher than that of RUT, histology and culture (91% vs 66%,43% and 37%, respectively; P = 0.01, ＜0.001, ＜0.001,respectively), but similar to that of serology (94%) and UBT (94%). Additionally, PCR exhibited a greater specificity than serology (100% vs 65%, P＜0.01). However, the specificity of PCR did not differ from that of other tests.Further analysis revealed significant differences in the sensitivities of RUT, culture, histology and PCR between the patients with and those without blood in the stomach (P＜0.01, P = 0.09,P＜0.05, and P＜0.05, respectively).CONCLUSION: PCR is the most accurate method among the biopsy-based tests to detect H pylori infection in patients with bleeding peptic ulcers. Blood may reduce the sensitivities of all biopsy-based tests.