Records were made of heart rates of 4 black bears, 2 males and 2 females, ages 1 to 42 months, weighing 0.6 - 70 kg. In the large bears, succinylcholine chloride was administered intramuscularly. The cubs were held while syringe needles connected to an EKG machine were inserted subcutaneously. It appears there is a marked fall in heart rate in black bears with increasing age until adulthood is reached. Succinylcholine vs. handling without anesthetic does not appear to be a factor in the results. Rates seem high, especially those of the larger, older bears. Though rectal temperature was normal, the excitement incident to anesthetic injection and the convulsive nature of its onset of action must be considered as factors in elevation of heart rate. Thus it seems possible that heart rates of the young bears are more reliable and that decrease in heart rate with age is even more marked than shown here.