The sarcoplasmic resistivity of long- and short-sarcomere muscle fibers in the walking leg extensor muscle of a crayfish (Orconectes virilis) was measured using a single intracellular microelectrode (the method of Dr. O. Schanne). For long-sarcomere fibers, the mean value was 143 ? cm; for short-sarcomere fibers, the mean value was 150 ? cm. There was no significant difference between the two values, but they differed from some given previously in the literature.