The distribution of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) has been investigated in a series of sections passing through the medulla oblongata and pons of the squirrel brain. A comparison of the two enzymes has given an interesting picture of their selective localization in the different nuclei. Marked AChE activity has been observed in the cranial nerve nuclei. BChE activity in various nuclei of the medulla oblongata and pons is variable and occurs diffusely between the cells. Possible reasons pertaining to marked variation in AChE and BChE contents of various nuclei and fiber tracts have been discussed.