Although many molecules are necessary for neuronal cell migrations in C. elegans, no guidance cues are known to be essential for any of these cells to migrate along the anteroposterior (AP) axis. We demonstrate that the fibroblast growth factor (FGF) EGL-17, an attractant for the migrating sex myoblasts (SMs), repels the CANs, a pair of neurons that migrate posteriorly from the head to the cent...