A peripheral nerve exudate, collected in situ from the proximal end of a severed rat sciatic nerve, can induce substantial axonal elongation from ganglion cells when tested on explanted adult rat retinae. The responsive cells are identified on the basis of their Thy 1.1 immunostaining properties. Similar outgrowth can be obtained from explants when the culture medium is supplemented with brain-derived neurotrophic factor (BDNF). In addition, both BDNF and the sciatic nerve exudate can prevent ganglion cell degeneration as shown by the retrograde transport of a fluorescent dye that had been applied to the superior colliculus prior to explantation. The results demonstrate that soluble components, released by lesioned peripheral nerves, can effect adult retinal ganglion cells in a way that is reminiscent of that which has been described in vivo using sciatic nerve grafts after sectioning of the optic nerve. The molecular nature of these components is discussed.