Four patients with sickle cell hemoglobinopathies (one sickle cell hemoglobin C disease (SC); three sickle cell trait (AS)) and hyphemas had a higher percentage of erythrocytes sickled in their anterior chambers than in their circulating venous blood. Intraocular pressure (IOP) was severely increased, 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 increase of IOP in sickle cell hemoglobinopathy patients may produced rapid deterioration of visual function, 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.