PIP: The sympto-thermal method is a temperature method of fertility control and includes the self-observation of symptoms of the ovulatory period, particularly the increased cervical mucus discharge. A rise in temperature must not be interpreted as ovulatory-related before the end of the cervical mucus discharge. The method of self-observation described is practical for about 90% of fertile women. The evaluation of the waking temperature graphs thus supplemented is easier and offers greater accuracy of prediction. In regard to avoiding conception, the sympto-thermal method offers effectiveness equal to the oral contraceptives. A review of 180 women with 3542 cycles in 1968 showed a use effectiveness of 0.7 unwanted pregnancies per 100 women years of exposure, without any method failure despite intercourse during postmenstrual infertile days. The method makes possible the consideration of individual peculiarities of the preovulatory phase including the possibility of ovulation prediction. If genuine menstruation has occurred a sterile phase is assumed in the beginning of the cycle through the 6th day. In sum, including consideration of patients' errors, the sympto-thermal method results in a failure rate (use-effectiveness) of 0.7/100 years of exposure.