The alignment and the movement of the eye is controlled by precise innervation of eye muscles by three cranial nerves: oculomotor nerve (nIII), trochlear nerve (nIV) and abducens nerve; alteration of the connectivity of these nerves can lead to strabismus and eye movement disorders. However, the molecular and cellular mechanisms that guide cranial nerve axons to the eye remain poorly understood. Our current project considers if Slit/Robo chemorepellent signaling guides the navigation of the oculomotor nerves. Oculomotor nerves develop in three main stages in mouse embryos, beginning with early nerve outgrowth from E9.5, pausing as a plexus of nerve fibers in contact with eye muscle precursors from E10.5-12.5, and final nerve branches reaching out and innervating specific eye muscles from E13.5-14.5. To test Slit and Robo functions in guiding oculomotor nerves, we mapped Slit and Robo expression, and traced nerve projections in Slit and Robo mutant mouse embryos. Slit1 and 2 surrounded nerves during outgrowth and branching around the eye, but also Slit2 was expressed in oculomotor neurons themselves; Robo1 and 2 were co-expressed by oculomotor axons. Robo1-/- 2-/- and Slit 1-/- 2-/- mutant embryos from embryonic stage (E)9.5 to E14.5 showed similar and severe errors in all three steps of motor nerve development. The early nerve was defasciculated, followed by failure to pause at the plexus, and strong disruptions to branches to muscles. To test the cell autonomous functions of Robos, we studied motor neuron-specific knockouts, which also showed severe errors at all three steps. Motor axons also required autonomous function of Slit2, suggesting that paracrine Slit signals promote motor nerve fasciculation, stimulate adhesion with muscle precursors, and guide nerve branching patterns to muscles. Our results suggest that Slit/Robo signals control multiple steps that are critical for oculomotor nerve development, including axon-axon contacts, axon-muscle precursor contacts, and potentially selective recognition signals to innervate specific muscles.