Four patients with sickle cell hemoglobinopathies (one SC, three AS) and hyphemas were found to have more erythrocytes sickled in their anterior chambers than in their circulating venous blood. Intraocular pressure was severely elevated, despite relatively small amounts of intracameral blood. Systemic hypotensive agents were not always successful in reducing IOP, and in patients with sickle cell hemoglobinopathy, are probably contraindicated in high or repeated dose regimens. Moderate elevation of IOP in sickle cell hemoglobinopathy patients may produce rapid deterioration of visual function, perhaps because of a greater than usual effect on vascular perfusion in the central retinal artery and optic nerve. Early anterior chamber paracentesis may be the best treatment for this type of hyphema-induced secondary glaucoma.