The relationship between stress, salivary flow rate and oral volatile sulfur-containing compounds (VSCs) is not clearly established. Two stressful situations were studied: psychological stress caused by a biochemistry examination (Study I) and psychophysiological stress caused by premenstrual syndrome (PMS) (Study II). Seventy-one undergraduate dental students took part in Study I and VSCs were measured 1 wk before the examination, on the day of examination and 1 wk after. In Study II, 50 women were selected (23 with and 27 without PMS) and the measurements were made during non-menstrual, premenstrual and menstrual stages. Unstimulated salivary flow was determined in the subjects of both studies. On the day of the biochemistry examination, VSCs significantly increased and salivary flow decreased compared with baseline values. Women with PMS showed higher VSC concentrations during the premenstrual stage than those without PMS (P < 0.05), but the salivary flow was not statistically different. A change in VSCs was observed during different stages of the menstrual cycle for the groups of women, but the salivary flow did not change. The results suggest that a stressful situation can be a predisposing factor for the increase of VSCs in the mouth air, but the mechanism cannot be simply explained by reduction of the salivary flow.