While planning medical care, health care workers must consider the body temperature changes as measured by the mothers on most occasions. We evaluated the reliability of three different temperature measurement methods when they were used by the mothers by comparing with the measurements taken by the pediatrician. In this prospective study, body temperatures of 50 healthy newborns during their 2nd day of life were measured by mothers and one physician with mercury-in-glass (MG), digital mercury (DM) and infrared tympanic membrane thermometers (ITMT). Measurements by the mothers and the physician were correlated for the three different methods. The effects of the educational level of the mothers and the presence of children at home on the reliability and the number of differences > or = 0.5 degrees C were also evaluated for each of the methods. In comparing the measurements by the mothers and the pediatrician, correlation coefficient was 0.12 in MG thermometer readings, 0.23 in DM thermometer readings and 0.78 in ITMT readings, meaning that tympanic measurements by the mothers and the pediatricians were more correlated (p < 0.0001). The means and ranges of absolute differences of MG, DM, and tympanic thermometer measurements were 0.43 +/- 0.42, 0-1.7; 0.36 +/- 0.45, 0-2.2; and 0.13 +/- 0.12, 0-0.7 degrees C, respectively. The number of measurements with an absolute difference > or = 0.5 degrees C was 17 in MG readings, 11 in DM readings, and 1 in ITMT readings, The educational level of the mothers and the presence of children at home had no effect on the correlations. The intraclass coefficient for the three sets of measurements by the pediatricians was 0.91. Body temperature measurements in newborn babies as taken by their mothers were more correlated with the readings by the pediatricians when the ITMT was used. Tympanic thermometers seem to be useful for the mothers of any educational level and are independent of having experience with a previous child. The ease of use and short calibration time for reading are also advantageous for these thermometers.