Reticulitermes flavipes(Kollar) (third and fourth instar) workers from a laboratory colony were subjected to 0°C for either 10 or 30d after having been exposed to 10°C for varied periods from 0 to 30d. Worker mortality increased with increased exposure to 10°C. The lowest percentage of mortality was observed in workers exposed to 0°C for 10d after 0d of 10°C acclimation. Workers exposed to 0°C for 30d exhibited high mortality rates regardless of the duration of the 10°C acclimation periods. The supercooling point of laboratory reared termite workers generally increased with prolonged exposure to 10°C. Termite workers subjected to 0°e for 10d did not exhibit lower supercooling points following increased acclimation periods at 10°. However, termites subjected to 0° for 30d generally did exhibit decreased supercooling points following increased exposure to acclimation temperatures at 10°C. Lower lethal temperatures were higher than the super cooling points for laboratory workers exposed to 10°C for 0, 1, and 10d and for field collected workers during the months of May to July 1992. However, lower lethal temperatures were lower than supercooling points for laboratory termites exposed to 10° for 20 and 30d and for field collected termites during the months of September to November 1992. These data indicate that 10°C cold acclimation ofR. flavipesdoes not result in lower supercooling points in either laboratory maintained or field collected samples. However, decreased lower lethal temperatures in response to either cooler seasonal temperatures or longer exposure does indicate that a switch from prefreeze mortality to freeze tolerance may be occurring.