Increase in temperature elicits an increase in the number of nerve impulses arising spontaneously from deafferented crayfish ganglia. This alteration in gross frequency gives an apparent temperature characteristic of 27,000 calories. Changes in the number of active fibers and in the frequency of discharge of individual units account for the alterations in the gross frequency. The change in number of active units gives a n value of 17,500 calories. Individual fibers fall into two groups with respect to the effect of temperature on their frequency of discharge. One of these groups exhibits a µ value of 14,500 calories and the other yields a µ value of 7,000 calories.