A prospective, blind study was carried out on 44 patients to evaluate the most suitable time to perform transvaginal sonohysterography. On the day of arrival at our unit, regardless of their cycle day, the women underwent sonohysterographic evaluation, which was repeated during the first 10 days of the next cycle. Patients with sonohysterographic findings underwent hysteroscopy. According to the timing of the first examination, they were divided into two groups, i.e. group 1 for the first 10 days of the cycle, and group 2 for days 16 through 28. At the end of the study the groups were compared. The results showed a false-positive rate of 27% in group 2, while no false-positive was found in group 1. We concluded that the best time for sonohysterography in patients who still have their menstrual period is during the first 10 days of the cycle.