With the histochemical immunofluorescence technique were demonstrated the insulin and glucagon in the transplantated isolated Langerhans' islets in the liver at diabetic rats and dogs. Further on were tested the diabetic metabolic level with aid of clinico-chemical methods during the period of investigation (blood glucose, serum insulin, glucose tolerance test). It was found that after transplantation, 1 year by the rats and more than 8 weeks by the dogs, is existing a normoglycemic level. In the transplanted islets were seen a good immunofluorescence of insulin in the B cells and the glucagon in the A cells in all investigated stages.