Pathologic halitosis has been classified into 5 types: oral, airway, gastroesophageal, blood-borne and subjective, respectively. Type 1 (oral) halitosis mostly takes origin from anaerobic bacterial activities on oral surfaces. The role of anaerobic bacterial activities is clearly demonstrated, but despite the large number of anectodal claims, the role of Candida in patients with halitosis has not been adequately investigated. The aim of this study was to confirm the relationship between Candida and halitosis. A total of 136 subjects were enrolled and divided into two groups. The study group comprised of 69 patients with halitosis who had over 0.7 ppm H2S concentration in their oral cavity and the control group comprised of 67 healthly subjects. Self assesment scores for halitosis, Candida colony counts in saliva samples, oral NH3, SO2, H2S, H-2 and volatile organic gas concentrations were recorded. H2S producing capacity of subjects was quantified by applying cysteine challenge test. Candida samples were taken from the mouths of the patients with and without halitosis, and Candida albicans isolates were inoculated into broth medium. After 3 days of incubation at 37 degrees C, gas concentrations of the headspace of the flasks were read by a portable multigas detector. The rate of Candida positivity was 44.9% in the study group while it was 46.3% in the control group. There was no statistical significant difference between the groups according to the Candida growth (p=0.561). The oral gas concentrations were comparable in both groups (p<0.05). Oral H2S concentration increased 9.65 fold with 20 mM cysteine rinse in patients with halitosis while it was increased 5.8 fold in controls. Self assesment for halitosis were well correlated with clinical signs (p=0.001, r=0.8). Concentrations of hidrogen and organic gases were found to be increased in all Candida culture media. In this study, no relationship between the presence of Candida and oral halitosis was detected. As a result, there is no need for diets similar to Candida diet in the treatment of halitosis. On the other hand, cysteine challenge can be a useful diagnostic tool. In addition, portable gas detectors can be used as a convenient and practical halitometer to quantify halitosis.