Prior studies have produced conflicting results about whether a change in electric potential occurs at the time of ovulation. This study was undertaken to determine whether the Ovutron, a digital voltmeter which displays the sign and magnitude of voltage measured when the index fingers are applied to the electrodes, would produce a mix in polarity, some positive and some negative voltages, with 5 consecutive measurements preceding ovulation. This device was used daily in 10 normally ovulating women to determine whether such a mix in polarity occurred during the menstrual cycle and its relationship to the corresponding daily measurements of luteinizing hormone, total immunoreactive estrogen (IRE) and progesterone heralding and confirming ovulation. In addition, the Ovutron readings were compared to the basal body temperature (BBT) measurements. In 8 of 10 women studied with the Ovutron device, a mix in polarity was observed in 2 of 3 consecutive days preceding ovulation and was associated in all but 2 subjects with a 50 pg/ml/day incremental increase in IRE. By comparison, only 4 of the 10 subjects had a "classic" biphasic BBT curve. This novel device should be evaluated in a large group of women employing these and other additional parameters (e.g., ultrasonography) in order to determine its efficacy and whether it has a role in the treatment of infertility as well as contraception.