Tamoxifen, an effective treatment of breast cancer, has been shown to cause ocular toxic effects. The purpose of this study was to determine retinal toxicity by full-field and focal electroretinograms (ERGs) in patients treated with tamoxifen. Fullfield and focal ERGs were obtained from three groups: Tamoxifen-14 females (47-72 years, mean 58.3 + or - 9.1) with normal fundus, treated with tamoxifen from 2 to 37 months; No Treatment-10 females (39-65 years, mean 50.1 + or - 8.7) with previous breast cancer diagnosis and before tamoxifen treatment; Control-13 normal female volunteers (41-81 years, mean 52.7 + or - 12.1). Peak-to-peak amplitude and b-wave implicit time were measured and statistically analyzed.Mean peak-to-peak amplitudes and implicit time from full-field and focal ERGs were comparable for the three different groups. Low-dosage tamoxifen showed no retinotoxic effect assessed by full-field and focal ERG in this small group of women with breast cancer.