Concurrent and construct validation of the OMNI Scale of Thermal Sensations was examined in a sample of 16 adult men and 5 adult women. Concurrent validity was established by regressing OMNI ratings of thermal sensation against core and skin temperatures obtained during treadmill walking while wearing firefighter thermal-protective clothing in temperatures between 33 and 35 degrees C. Construct validity was established by regressing the OMNI scale against a construct-specific visual analogue scale. OMNI scale responses accounted for statistically significant variance in both skin temperature and core temperature (48% and 51%, respectively) and visual analogue scale responses (84%). Concurrent and construct validity were established for the OMNI Scale of Thermal Sensations in healthy adults performing treadmill walking while wearing fire fighter thermal protective clothing.