The small rise in basal body temperature (BBT) during the menstrual cycle is often used as an indicator that ovulation has occurred and that a period of infertility has begun, When this information is used for either conception or contraception, it is important determine this thermal rise reliably and with a minimum of uncertainty. This is often difficult because the biphasic shift and the day-to- day variability are of similar magnitude. Of the non-physiological factors that contribute to temperature variability in BBT measurements, site selection and user technique appear to play a dominant role. The urine temperature appears to be free of many of these perturbing factors which scatter the BBT data obtained when using oral, rectal or vaginal measurements and presents an opportunity to detect the biphasic shift with greater reliability. The purpose of this research is to design, construct and test in- vitro and in-vivo a limited range, high resolution, multi-sensor liquid crystal thermometer (LCT) which is incorporated into a light-weight plastic housing used to direct the flow or urine over the LCT. The successful development of this product will allow women to obtain more accurate BBT curves which are easier to interpret. This advantage coupled with the benefits of the speed and ease of use of the device will lead to a substantial improvement in the efficacy of natural family planning methods involving BBT measurement.