Abstract The electrical “cable” properties of fibers in the soleus muscle of normal and dystrophic mice were measured in vitro at 37C with intracellular microelectrodes. The motor nerve of the dystrophic muscle was stimulated to determine whether or not the fibers chosen for measurement were functionally innervated. Normal and dystrophic muscles which had been surgically denervated were also studied. Specific membrane resistance was higher in normal than in dystrophic muscle fibers; the respective mean values were 1516 and 636 ohm cm 2. Dystrophic fibers which were not functionally innervated had significantly higher resistance than those which were innervated, but in neither case did values approach the normal. In both normal and dystrophic muscles, previous sectioning of the motor nerve led to an increase in muscle fiber input resistance. Surgically denervated dystrophic fibers had considerably higher resistance than measured in fibers which had become functionally denervated during the course of the disease. The results suggest that denervation per se cannot account for the differences between normal and dystrophic muscle fibers.