Background/Aims: Urea breath test(UBT) is known as most specific and accurate non invasive method to detect Helicobacter pylori infection. ¹³C-UBT is popular method of UBT, but it is complex to analyse and expensive. On the contrary ¹⁴C-UBT system is relatively simple and quick in-office analysis and inexpensive. Methods: 50 patients(M：F=20：30, mean age 51.5⁑14.6) underwent ¹⁴C-UBT, rapid urease test and gastric biopsy pathology on the same day. The results of ¹⁴C-UBT were compared with that of gastric biopsy pathology and rapid urease test. Results: We assessed the sensitivity, specificity, positive predictive value (PPV), negative predictive value(NPV) and accuracy of ¹⁴C-UBT, all are 100%. And the quantitative value of ¹⁴C-UBT were compared with the pathologic grade of pathology, a significant correlation was found between them. Conclusions: We found that ¹⁴C-UBT is highly accurate and simple noninvasive method for diagnosis of Helicobacter pylori infection and reflect the degree of bacterial density. (Korean J Helicobacter Res Prac 2002;2:165-169)