Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The menstrual cycle has been pointed out as a factor influencing halitosis. However, this relationship has not yet been clarified. The aim of this study was to evaluate the influence of gender and the menstrual cycle on the production of volatile sulphur compounds (VSC) in women (n = 14) across the menstrual cycle, and in men (n = 17). Volunteers in good oral and general health were submitted to the evaluation of VSC, salivary flow, cortisol and anaerobic bacteria counts in saliva. Data were compared among groups by Analysis of Variance (alpha = 5%). VSC was higher in the menstrual and premenstrual phases when compared with men and the follicular phase (p < 0.05). Salivary flow was lower in the menstrual and premenstrual phases when compared with men and the follicular phase (p < 0.05). Salivary cortisol was higher in the menstrual phase in comparison with men and the premenstrual and follicular phases (p < 0.05). Total salivary protein was higher in men when compared to women (p < 0.05) with no differences among menstrual phases (p > 0.05). Levels of anaerobic micro-organisms, however, were not different among groups (p > 0.05). In conclusion, the production of VSC is influenced by menstrual cycle and protein concentration and salivary flow might be involved in this process. (C) 2008 Elsevier Ltd. All rights reserved.531211071112Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [04/062982, 03/11592-4, 05/54751-0]