Conduction velocity of the ventral caudal nerve was determined in vivo in 2 groups of rats previously adapted to 2[degree] and 5[degree]C, respectively. A decrease was noted in conduction velocity most noticeable at warmer tail temperatures, above 20 C, as was previously reported. Continued exposure of the animals to cold however, results in recovery of nerve function to the normal state. Impairment in function and subsequent recovery may be part of the adaptation process.