Combined transplantation of fetal pancreas and thymus was performed in 10 patients suffering from severe diabetes I. They were closely followed for over one year, and it was found that among them 7 showed spectacular clinical improvement, including 2 with total discontinuation of insulin, and 5 with average reduction of insulin by 82%. In 3 patients, the dosage of insulin was reduced by an average of 56.9%. The average reduction of insulin for the 10 patients in 2 months, 6 months and one year after the transplantation was 68.3%, 74.5%, and 78.4%, respectively. The effect of warm ischemia of different durations on the donor tissues was studied with electron microscopy. The significance of combined transplantation and the relationship of the techniques of procuring the donor tissues and transplantation is discussed.