Introduction: Nasal stuffness is a great problem for many women in the later part of pregnancy. Objective: This study was performed to evaluate whether oestrogen causes nasal congestion and/or a hyperreactive reaction of the nasal mucosa. Material and Methods: Ten healthy fertile women were examined during menstruation. Nasal mucosal congestion was studied with rhinostereometry and acoustic rhinometry. The nasal mucosa was challenged with 3 doses of histamine solution to study nasal reactivity. Measurements were made 3 times during menstruation. To find the exact time of ovulation, when oestrogen reaches its peak value, intravaginal ultrasound tests were done and blood samples taken, to determine the oestrogen and progesterone levels. Results: The nasal mucosa became hyperreactive to histamine in connection with ovulation, when the blood level of oestrogen reached its peak. This does not occur during the menstrual or the luteal phase. No significant alteration was found in the baseline position during the menstruation. Conclusion: There is a connection between high oestrogen level and nasal mucosal reactivity.