There is disagreement about a possible relationship between Helicobacter pylori (H. pylori) infection and objective halitosis, as established by volatile sulfur compounds (VSCs) in the breath. Many studies related to H. pylori used self-reported halitosis, a subjective and unreliable method to detect halitosis. In this study a possible relation between H. pylori and halitosis was evaluated, using an objective method (gas chromatography, GC) to detect the VSCs, responsible for the halitosis. The levels of the VSCs hydrogen sulfide (H(2)S), methyl mercaptan (MM) and dimethyl sulfide (DMS) were measured in mouth breath and in stomach air of 11 H. pylori positive patients and of 38 H. pylori negative patients, all with gastric pathology. Halitosis was also established by organoleptic scoring (OLS) of mouth-breath. The levels of H(2)S, MM and DMS in the mouth-breath and stomach air of the H. pylori positive patients did not differ significantly from those of the H. pylori negative patients. OLS of the mouth-breath resulted in 9 patients with halitosis, 1 out of the H. pylori positive group and 8 out of the H. pylori negative group, which is not statistically different. The concentrations of the VSCs in stomach air were in nearly all cases below the thresholds of objectionability of the various VSCs, indicating that halitosis does not originate in the stomach. The patients with gastric pathology were also compared with control patients without gastric pathology and with normal volunteers. No significant differences in VSCs in mouth breath were observed between these groups. Thus, in this study no association between halitosis and H. pylori infection was found. Halitosis, as established by GC and OLS, nearly always originates within the oral cavity and seldom or never within the stomach.