It has been shown both experimentally (Stockbridge, N., and L. L. Stockbridge. 1988. J. Neurophysiol. 59:1277–1285) and theoretically (Stockbridge, N. 1988. J. Neurophysiol. 59:1286–1295) that the second of two closely spaced action potentials may be differentially conducted into a short daughter branch. Using numerical methods, the response to trains was examined in axons with a single bifurcation and uniform membrane properties. Short daughter branches conduct at higher rates of stimulation than do long branches. Under some conditions the longer daughter branch is always silent. Under other conditions, one or both branches will begin to conduct action potentials only when the stimulus frequency is high enough.