A complete, commercially available, integrated telemetry and data acquisition system designed to measure core body temperature (BT) was evaluated in a total of 45 growing pigs from 95 and 150 days of age. This system is composed of an implantable pill that wirelessly and continuously transmits BT to a dedicated recorder. Pills were surgically implanted in the brachiocephalic muscle (neck) at 3 to 4 cm in depth. Measurement interval of BT was set at 2 min. Pigs were housed in individual pens and were allocated to 5 experimental groups (G). The G1 group of pigs was kept at 22°C from 100 and 150 days (d) of age, G2, G3, G4 pigs were submitted to an experimentally thermal challenge (5 d at 32°C) from 103, 117, 131 d of age, respectively. The G5 group was thermally challenged at the 3 consecutive stages. For G1 pigs, average daily BT varied considerably among animals (from 38.3 to 39.0°C) and decreased linearly with BW. BT exhibited circadian rhythms with 2 peaks (between 05:00 and 11:00 h and between 12:00 and 19:00 h). The occurrence of peaks was normally congruent, within a 2-h window, across pigs. Daily average BT increased during the thermal challenge (39.5 vs. 38.7°C; P < 0.01). At 32°C, the circadian rhythm of BT changed with a minimal (39.1°C) and a maximal value (40.0°C) at 09:00 and 22:00 h, respectively. Measurements of BT assessed by telemetry and by a rectal thermometer were well correlated (r = 0.71) but rectal temperature appears to be underestimated as BT decreased. The telemetry system was found to be a viable alternative for a continuous monitoring of BT in a research setting.