Background. Defining tolerable warm ischemia (WI) is mandatory before nonheartbeating cadavers can be used to enlarge the donor pool. No studies to date have precisely evaluated the effect of pancreatic WI on islet yield and viability in a large animal model. Methods. We used mongrel dogs in our study at the University of Minnesota. Excised pancreases were left in situ for a designated period (0, 30, 45, and 60 min in groups 1 to 4, respectively) of WI. Then, they were digested by the automated collagenase digestion method of Ricordi, purified on Euro-Ficoll discontinuation gradients with the COBE cell processor, and autotransplanted into the liver via a mesenteric vein. We compared the four groups in terms of islet yield, expressed as islet equivalents (IE; diameter standardizing to 150 μm) per pancreas weight (IE/g pancreas), and viability, assessed by functional success (maintenance of normoglycemia for 2 weeks) after transplant. Results. Mean islet yield (± SD) and the functional success rate after transplant were as follows: 6200±1800 IE/g pancreas and 4 of 4 (100%) in group 1; 6300±4400 and 4 of 4 (100%) in group 2; 3800±2600 and 2 of 4 (50%) in group 3; and 1400±1300 and 0 of 4 (0%) in group 4 (P=0.01 vs. group 1). Conclusions. With 30 min or less of WI, there are no deleterious effects on islet yield and viability. However, with periods of WI longer than 30 min, the loss in islet yield is severe, resulting in functional failure after autotransplantation. The limit of WI that is tolerable for islets is shorter than for a whole pancreas.