Adult mammalian central nervous system (CNS) neurons fail to regenerate after injury. Both the extracellular environment and the intrinsic growth state of neurons affect their ability to regenerate. The cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF), known to promote cell survival, may also activate cellular growth programs. In this thesis, the effect of GM-CSF on CNS neurite growth was investigated. The retina, an easily accessible region of the CNS, was examined. Pieces of retinal tissue – retinal explants – were maintained in culture and varying doses of GM-CSF were applied. The growth of retinal ganglion cells (RGC) neurites was quantified. The results indicated that GM-CSF enhanced lengthy neurite growth in embryonic mouse retinal explants. The retinal explantation technique optimized in this study could be used to test the role of potential agents in growth-promotion. Ultimately, long-distance neuronal regeneration is critical in functional recovery after neural injury.