13 mongrel dogs, weighing from 12 to 25 kg were subjected to substitutive allotransplantation of the duodenopancreas and survived for over 48 h. Immunodepressive therapy consisted of azathioprine and phytohemagglutinin. Tissue compatibility has been evaluated by 3 different methods. Average survival time (34.7 days) and survival time in each histocompatibility group were longer than in the comparative series of 21 dogs receiving azathioprine, corticoids and antilymphocyte globulin (28.1 days). Lower incidence of infection and specific immunodepressive action of the PHA explains better results obtained by the association of azathioprine and PHA after pancreatic allotransplantation in the dogs.