Two transplant procedures have been investigated in which one third of the pancreas was autotransplanted into the splenic pulp of dogs. The two procedures consist of simple mechanical dissociation of the pancreas or mechanical dissociation followed by collagenase digestion. The ability of the endocrine segment of the transplant to survive and function was assessed by stimulation with arginine and measurement of insulin and glucagon response. The results demonstrate that both transplant procedures result in functioning beta and alpha cells that rapidly secrete both insulin and glucagon in response to arginine stimulation. However, greater insulin responses were obtained when mechanically dissociated but nonenzyme digested pancreatic tissue was used for transplantation. The spleen appears to be an excellent transplant site for the reception of endocrine pancreatic tissue and allowed both beta and alpha cells to survive following transplantation.