This investigation was undertaken to study the variations in gingival fluid flow during the menstrual cycle in a group of young females. The material consisted of 17 female student nurses, 19‐23 years of age (mean 19,8 years) with eight male students, aged 20‐23 (mean 21,9 years) acting as controls. The mesial aspects of the buccal mesial gingiva of five maxillary incisors and canines were examined. Intra‐crevicular sampling of gingival fluid was performed in accordance with the technique described by Brill (1959) and Egelberg (1964). The day of ovulation was determined by cytologic examination of oral scrapings. The mean exudate values on the five menstrual days were 0.8, 0.8, 0.8, 0.8 and 0.9. The corresponding value on the day of ovulation was 1.2. The difference between the exudate values of the menstrual phase and the ovulatory day is statistically significant at the 0.1 per cent level. In the group of male students there was no significant difference between the fluid scores from various test days and periods of days. The data from the present investigation show that, in young females, there are variations in amount of gingival fluid, which can be correlated to the different phases of the menstrual cycle.