N-acetyl-beta-D-glycosaminidase (NAG) isoenzymes were studied in 28 insulin-dependent diabetics. After electrophoretic migration isoenzyme. A levels were higher than in healthy controls. This suggests that the increase in total serum NAG in diabetics is due to a specific increase in this enzyme. A comparison of these results with those of other authors suggests that NAG alterations are specific to various pathologies.