Studies have been conducted on 72 rats to determine the most suitable temperature at which rapid rewarming should be done as an immediate treatment for frostbite. Animals were put in a harness containing arrangements for warming the body. Their hind limbs were left out of the harness. They were then exposed to -15 degrees +/- 1 degrees C in a deep freeze for 60 min, during which paw temperature was recorded every 5 min. After this, the animals were taken out, the left hind limb was rapidly rewarmed in a water bath maintained at 35 degrees, 37 degrees, 39 degrees, 41 degrees, 43 degrees, or 45 degrees C for different batches and the right hind limb was left free for slow rewarming at room temperature (27 degrees -29 degrees C). The severity of cold injury in the two limbs was compared. The paw temperature showed a drop on cold exposure, followed by a rapid rise and then a second fall. The degree of injury was related to the duration of exposure after the rise in the paw temperature. The rapid rewarming was effective only at water bath temperature of 37 degrees-39 degrees C and was harmful at 45 degrees C. This shows that rewarming at about body temperature is most effective as immediate treatment for frostbite.