13C-Urea breath tests (UBT) were performed in 217 patients with epigastric symptoms to assess (a) the validity of shorter intervals of breath sample collection and (b) of the non-fasting state on diagnosing H. pylori infection and to evaluate (c) a more simple sampling method. (a) In 186 patients, breath samples were taken before and at 10, 20, 30, 40, 50, 60, 90, and 120 minutes after ingestion of 75 mg 13C-urea. 13C-enrichment was measured by isotope ratio mass spectrometry [delta/1000] and the cumulative recovery rate (CRR) was calculated. (b) 31 patients performed 13C-UBTs on two occasions, i.e. fasted and in the postprandial state collecting breath before and 30 min after substrate ingestion. (c) 61 breath samples were obtained in duplicate, i.e. both with an aluminium foil breath bag using evacuated glass tubes, and by exhalation into open vials via straw. (a) DOB-responses at 10, 20, 30, and 40 minutes after dose showed a linear correlation with the 120 min-CRR. Referring to a CRR > 3% at 120 min (criterion of H. pylori-infection), DOB-responses at 20 min with a cut off-value at 5/1000 (ROC-analysis) were shown to be valid for diagnosing H. pylori status in man (sensitivity 99.0%, specificity 100%). (b) Postprandially, mean DOB-responses of H.pylori positive patients were lower than in the fasting state (17.46/1000 vs. 27.63/1000; p < 0.01). With the cut-off at 5/1000, however, sensitivity still was 94.4% and specificity was 100%. (c) The straw and breath bag method gave equivalent results (r = 0.98, p < 0.0001). (a) A two sample measurement using the DOB at 20 min and a cut-off value of 5/1000 can replace the CRR-calculation over 120 minutes. (b) Although quantitative DOB-responses are significantly affected, 13C-UBT can be performed in the postprandial state with no significant effect on the detection of the H. pylori infection. (c) The sample collection by a simple straw method meets precision requirements < 1.5 delta/1000. Thus, the 13C-UBT can be performed cheaper, faster and more conveniently.