We investigated the tolerance of human recombinant interleukin-1β (IL-1β) injected intravitreously and its putative role in the clearance of experimental vitreous hemorrhages. Three groups of 10 pigmented rabbits each were injected intravitreously with 0.1 ml autologous whole blood. Mean fundus revisualization times after blood clouding were as follows: group 1 (controls, blood injection only), 5.3 weeks; group 2 (100 units of IL-1β injected intravitreously 7 days after blood injection), 3.3 weeks; group 3 (1,000 units of IL-1β injected intravitreously 7 days after blood injection), 3.2 weeks. Group 4 (10 rabbits) was injected only with 1,000 units of IL-1β. Clinical examinations showed a transient mild inflammatory reaction in group 2 and a transient severe reaction in groups 3 and 4. Vitreous opacities, a whitish retinal reaction and vascular changes were seen in group 4. Electroretinography did not show a b-wave decrease in any group. These results suggest that low concentrations of IL-1β may be useful for nonsurgical treatment of human vitreous hemorrhage.