Although several papers on the urea breath test have been published, some methodological questions are still unsolved: the dose of 13C-urea, the test meal composition, the breath sampling, the fasting or fed condition, the postural settings, and the cut-off points. Moreover, special conditions, such as those occurring in paediatric and uraemic patients or subjects with previous gastric surgery should be borne in mind when evaluating the 13C-urea breath test results. This review focuses on methodological problems and potential pitfalls which can affect the accuracy of the 13C-urea breath test.