Pancreas transplantation was studied in the dog using a total duct ligated pancreas as allograft. In a group of 10 mongrel dogs the effects of longterm (6–36 months) total duct ligation on the endocrine pancreas function were studied by means of repeated intravenous glucose tolerance tests (iv-GTT). One year after total duct ligation the mean glucose assimilation coefficient (k-value) was 75%, the median insulin peak value (IPV) 63% and "total" insulin secretion in the first thirty minutes (TIS) 58 % of the pre-operative values. These levels were maintained up to three years after duct ligation. The total duct ligated pancreas was then used as an allograft in 28 beagles in order to study the influence of DL-A (dog leucocyte-antigens) matching on the survival time of the graft. DL-A identity compared to one or two haplotype diference gave a fourfold increase in median survival time from 9 to 40 days. In a second group of 14 beagles with one haplotype difference the effect of immunosuppressive therapy was studied. The methods used (antilymphocyte serum and a combination of prednisone and azathioprine) increased the median survival time to the level seen in DL-A identity. In conclusion the total duct ligated pancreas can be used as an insulin secreting allograft, providing rejection can be suppressed adequately.