The clinical significance and potential of respiratory tests for diagnostics of Helicobacter pylori infection was estimated in 76 patients. Results of 13C and 14C-urease tests were in especially good agreement with those oh histological studies. The 13C-urease test should be preferred in the examination of both in-patients and out-patients whereas NH3-urease test is much inferior to 13C and 14C-urease tests in terms of informative value.