During a prospective screening for proteinuria in diabetic patients, isolated Bence-Jones proteinuria was detected in 2 cases. The first patient, a 52-year-old black female, was seen for evaluation of a slow but progressive weight loss which was attributed to poor adjustment of insulin therapy. The patient gained weight after an increase of the daily insulin administration. She had plasmocytosis in a bone marrow aspirate, but no other evidence of myelomatosis. The second patient, a 59-year-old black male who was seen for routine evaluation of his diabetes, had no clinical or laboratory evidence of myelomatosis. Although precise definition of these cases as "benign" or "idiopathic" Bence-Jones proteinuria is impossible without prolonged follow-up, at the time of presentation they appeared to fit this classification. This observation is one further example that isolated Bence-Jones proteinuria may be seen without any evidence of malignant B-cell dyscrasia.