Four cases of ocular injuries induced by mistaken instillation of Rokushingan pills, a traditional Japanese medicine, to the conjunctiva and cornea were reported. Conjunctivitis, corneal edema, Descemet’s folds and temporary decrease in vision were found. These findings disappeared without sequelae within 10 days. The ocular lesions were considered to be caused by Bufonis venenum, which is one of six crude biological extracts in the drug, and is known to contain an inhibitor of Na＋ ,K＋ - adenosine triphosphatase. All the patients, aged between 53 and 78 years, were treated with either age-related cataract or glaucoma for 3 to 18 years. They confused the container of Rokushingan with that of their daily eyedrops because of the similar sizes and shapes of the bottles. Ophthalmologists should be aware of such cases and the measures to avoid such mistaken instillation should be seriously considered.