Ephaptic transmission was observed between spontaneously active single nerve fibers in the spinal nerve roots of dystrophic mice. In 5 ephaptically interacting pairs of fibers the conduction velocities were < 1 m/s in the exciting fibers and were 2-10 m/s in the excited fibers in the immediate vicinity of the ephapses at 26-28.degree. C. Membrane current analysis implied conduction was continuous in the exciting fibers. In some cases conduction away from the ephapse in the excited fiber was saltatory in at least one and possibly in both directions of transmission. In some cases the direction of ephaptic transmission apparently was from bare axon to myelinated axon. Transmission time across the ephapses, measured as the interval between peaks of inward membrane current in exciting and excited fibers, was .ltoreq. 100-240 .mu.s. Ephaptic transmission was not necessarily contingent upon the direction of propagation of the impulse in the exciting fiber. Ephaptic transmission between 2 fibers can remain stable at frequencies of at least 70 Hz. Multiple sites of spontaneous excitation may exist in single dystrophic mouse spinal root axons. An impulse transversing a site of ectopic excitation may incite a subsequent burst of impulses to arise from that site following a delay of more than 100 ms.