Adrenal medulla transplanted to the anterior chamber of the eye was studied by electron microscopy. Transplanted chromaffin cells consisted of noradrenaline cells, adrenaline cells and small granule-containing cells, and they formed long cytoplasmic processes. Some chromaffin cells were directly opposed to the iridial epithelial cells. A few adrenergic and cholinergic ganglion cells were seen in the transplant. Nerve fibres, mostly cholinergic, but a few adrenergic, were seen within satellite cells enclosing chromaffin and ganglion cells. A few synapses were formed on the chromaffin and ganglion cells, though the number of such synapses remained small even 6 months after transplantation. The possible origin of these nerve fibres, and the specificity of reinnervation are discussed.