A syndrome of nausea, vomiting, proteinuria, acidosis, glycosuria, and aminoaciduria was observed in three patients. The clinical picture at first resembled that of diabetes mellitus. The three patients, a 54-yr-old woman, a 13-yr-old girl, and a 13-yr-old boy, were found to have taken deteriorated preparations of tetracycline as treatment, respectively, for maxillary sinusitis, pharyngitis, and respiratory infection. The two children had received tetracycline on previous occasions without bad effects. All three patients recovered in about a month. A degradation product of tetracycline such as epi-anhydrotetracycline or anhydrotetracycline was probably the etiologic factor.