Body temperatures (T_b) of eight free-ranging Heterodon platirhinos were measured with radiotelemetry throughout the year. Body temperature ranged from 5–37°C and varied with air temperature and activity. During the active season, T_b of active snakes (∼30.5°C) averaged about 3°C higher than that of inactive snakes (∼27.4°C). Body temperature did not differ between the sexes or between resident and nonresident snakes. At air temperatures below 30°C, T_b averaged ∼3°C above air temperature; at air temperatures above 30°C, T_b averaged ∼0.2°C below air temperature. Basking appears to be important in the thermal ecology of H. platirhinos. Body temperature of free-ranging active H. platirhinos monitored with radiotelemetry was similar to previous reports on T_bs of active H. platirhinos measured with cloacal thermometers. A thorough knowledge of basic thermal requirements of H. platirhinos may be useful in its conservation.