Various ocular abnormalities have been reported in patients with thalassemia, and have been, for the most part, attributed to the toxic effects of high-dose desferrioxamine (DFO). We have performed an electroretinographic and visual-evoked potential (VEP) study in 31 thalassemic patients who had never received high doses of DFO. The abnormalities found were very similar to those reported in early siderosis bulbi and included a b1-wave of significantly higher amplitude at 1 min and at the alpha point. VEPs showed a N1-P1 amplitude significantly greater than in controls. These findings, which were more marked in older patients, point to an important causative role of iron in their genesis.