Chloramphenicol is a worldwide used bacteriostatic antibiotic, discovered in 1947 and known by its toxic and teratogenic effects. Its use is not recommended during pregnancy and lactation. Ocular malformations can occur during embryologic period if something interferes with the tissue formation and differentiation. Cataracts are the most common congenital lenticular anomaly in dogs. Three 45 days old Rottweiler puppies (2 females and one male) were taken to the Veterinary Hospital of University of Sao Paulo with bilateral nuclear partial lens opacities and were diagnosed with congenital cataracts. The owner related that their dam had received oral chloramphenicol (50mg/kg TID) during the first 30 days of pregnancy because of a suspected ehrlichiosis that was not confirmed by hematological and serological exams. Any other drug was administered to the bitch during this period. The puppies were submitted to complete systemic and ocular examination and no other anomalies were found. After 4 months the puppies were examined again and the lens opacity had became smaller and concentrated in thin lines. Vision was normal in all three puppies. Chloramphenicol toxicity and its teratogenic effects have being described in human patients since 1970's. The most frequent congenital anomalies found in human patients were undescended testis, cardiovascular disorders and low birth weight. Studies in rats treated with chloramphenicol during pregnancy determined the inhibitory effect on mitochondrial oxidative energy metabolism. The effect of chloramphenicol on lens opacity in vitro was described in 1989, in cultured rat lenses. To the authors concern this is the first report about chloramphenicol use during pregnancy associated with congenital cataracts in dogs.