Vascular abnormalities were studied in the eyes of 14 patients with sickle cell thalassemia (S-thal). Angioid streaks were observed for the first time in a patient with S-thal. "Black sunbursts," which are seen more often in the fundi of patients with sickle cell anemia (SS disease) than in those with sickle cell hemoglobin C disease (Hb SC) were generally few in number in the fundi of patients with S-thal. Proliferative sickle retinopathy, which is much more characteristic of Hb SC than of SS disease, was seen in nine patients with S-thal. The retinas of S-thal thus resemble those of Hb SC more than SS. The hemoglobin composition of a patient's red blood cells can be predicted, to a degree, from the presence and type of certain retinal anomalies in sickling disorders. Overall clinical status is not usually as good as indicator of hemoglobin composition.