Injection of Shigella endotoxin (2 mug) into the vitreous chamber of a normal rabbit eye induces on infiltration of polymorphonuclear leucocytes, miosis, a moderately intense dilation of iris, conjunctival and limbal vessels, and a breakdown in the blood-aqueous and blood-vitreal barriers. Significant amounts of soluble blood protein and prostaglandin-like (PG) material are found in the aqueous and vitreous humours withdrawn at 24 h. Endotoxin injected into the sensory denervated eye elicits similar vascular changes which appear to occur less rapidly than in normal eyes. conversely, the levels of aqueous and vireal PG-like material, as well as the capacity of excised irides to form PG from exogenous precursors, seems greater in the denervated eyes. If PG is an important mediator of ocular changes in the early phases, the results suggest that the action of this inflammatory autacoid in facilitating the ocular changes is less effective in eyes deprived of functional sensory nerves.