The sequence of events which follows the intravitreal injection of herpes simplex virus (HSV) into one eye has been observed as it affects the eyes, optic nerves, and optic chiasm. Initially the injected (right) eye showed an intense iridocyclitis and about 16 days after inoculation an exudative retinal detachment was observed. A similar sequence of events occurred in the uninjected (left) eye about 6 days later. HSV has been shown to pass along the right optic nerve towards the chiasm and from there down the left optic nerve. The primary route of spread appears to be via neuroglial cells rather than the axons. Tissue necrosis and re-myelination have been observed.