OBJECTIVE Postpartum diseases of sows are economically important in the pig industry. They affect animal health and welfare of sows and piglets. Measuring rectal temperature in sows post partum is a commonly used diagnostic method to early detection of infectious diseases. The study consisted of five parts. The objective of the first four parts was to evaluate the influence of different factors on the measurements of rectal temperature (e.g. investigator, thermometer, penetration depth of the thermometer). The secondary objective of this study was to validate the application of a temperature logger to continuously measure vaginal temperature. METHODS Thirty sows on the first day postpartum were used in the first four parts of the study. Rectal temperature was measured repeatedly by one investigator, by different investigators, with different thermometers and at different penetration depths. For the fifth part of the study 21 sows on the first day postpartum were used. A temperature logger was inserted in the vagina for a duration of 6 hours. Additionally, rectal temperature was measured. RESULTS The data showed that rectal temperature can be measured repeatably (mean ± standard deviation = 38.7 ± 0.1 °C, coefficient of variation = 0.2%). Different investigators or thermometers resulted in low differences (0.0 °C and 0.1 °C). The penetration depth of the thermometer influenced the result (difference of 0.4 °C between 5 and 10 cm). Rectal and vaginal temperatures, measured in 21 sows, were highly correlated (r = 0.80, p < 0.01) with a mean difference of 0.3 °C. CONCLUSIONS Rectal temperature measurement can be regarded as a repeatable diagnostic method. The measurement should be standardized (type of thermometer, penetration depth). The measurement of vaginal temperature with a data logger in early puerperal sows is a possible means for a continuous and non-invasive monitoring of body temperature.