Abstract: Defined changes in the volume of solution of ferric chloride used in titrating early morning urine have been used to predict ovulation during 81 menstrual cycles in 6 women. A peak volume of ferric chloride was formed in the middle of the menstrul cycle. The peak is compared with the LH peak of urine and with BBT. In addition, author have analysed urinary, estrogens during the menstrul cycle by HPLC. These results are coincident. Therefore, we can combine this method with BBT and cervical mucus to determine time of ovulation. The method can be also applied to predict ovulation in animals.

Key words: ferric chloride, ovulation, urine