After a circa 10-year therapy with MC-insulin NOVO 12 diabetics were changed to the chromatographically purified insulins L-insulin S.N.C. and insulin S.N.C. of the nationally-owned enterprise Berlin-Chemie. 3 and 6 months, respectively, ago after the ambulatory change the patients were metabolically, immunologically, hormonally and clinically characterized. Profiles of blood glucose, value of glycaemia and HbA1 also lipid parameters, creatinine values, residual B-cell function, blood pressure and ophthalmologic state did not show any significant differences to the initial values after change to S.N.C.-insulins. Insulin-antibody level (9.5%-9.4%-9.7%) and insulin need (0.48 IU/kg-0.46 IU/kg-0.48 Iu/kg) also remained unchanged. Local reactions were not observed. Under the condition of a permanently good quality of the S.N.C.-insulins (purity and stability of the preparations) the application of chromatographically purified insulin of the firm Berlin-Chemie with comparable therapeutic success as in insulin MC NOVO is possible in a large part of the patients.