Previous reports have suggested that gastrointestinal (GI) diseases may cause halitosis. The aim of this study was to evaluate the relationship between upper GI conditions, especially gastroesophageal reflux disease (GERD), and halitosis. PATIENTS AND METHODS: One hundred and thirty two consecutive patients complaining of upper GI symptoms were included in the study. All the patients completed a validated questionnaire that was designed to characterize and measure the severity of their symptoms. The questionnaire also contained questions about awareness and severity of oral bad breath. Following the filling of the questionnaire, the patients were physically examined and subjected to an upper GI endoscopy. RESULTS: The final diagnosis among the 132 patients (M/F = 70/62, mean age 45.2 years, range 20-87 years) was GERD in 72 patients (55%), Functional dyspepsia in 52 (39%), Peptic ulcer in seven patients (5%) and gastric cancer in one patient (1%). Halitosis was significantly associated with the occurrence and severity of heartburn (P = 0.027), regurgitation (P = 0.002) sour taste (P < 0.001), belching (P = 0.001) and borborigmus (P = 0.006). Halitosis was not associated with upper abdominal pain, bloating, early satiety and chest pain. In relation to the final diagnosis, halitosis was significantly associated only with GERD (P = 0.002) but not with functional dyspepsia (P = 0.855) and peptic ulcer disease (0.765). No correlation was found between Helicobacter pylori infection status and halitosis occurrence and severity (analysis of variance F = 0.001, P = 0.977). CONCLUSIONS: Halitosis is a frequent symptom of GERD and may be considered as an extra-esophageal manifestation of GERD. On the other hand, we did not find an association between functional dyspepsia, peptic ulcer disease and H. pylori infection with halitosis occurrence or severity.