We investigated glycemic stability and insulin requirement 1 month after a single transplantation of the islets from non-heart-beating donors or a living donor. Overall blood glucose levels decreased immediately after transplantation. The M-value and mean amplitude of glycemic excursions (MAGE) decreased significantly from 53.0 (range, 8.9-91.0) to 4.2 (0.6-8.8, P < 0.05) and from 8.5 mM (4.8-11.7) to 3.3 mM (2.0-4.5, P < 0.05), respectively. The values after transplantation were lower than the first quartile of 102 type 2 diabetic control patients. The estimated HbA(1c) level decreased significantly from 7.9% (5.7-10.9) to 5.4% (4.7-5.9, P < 0.05). The supplement of basal insulin decreased 43% from 0.31 units/kg/day (0.16-0.37) to 0.18 units/kg/day (0-0.22, P < 0.05). while that of stimulated insulin did not decrease significantly, from 0.28 units/kg/day (0.13-0.51) to 0.21 units/kg/day (0-0.41). Thus, only one islet transplantation can be sufficient to attain metabolic stability, probably by effective supply of basal insulin secretion, sufficient to avoid life-threatening severe hypoglycemia and prevent or delay the progress of secondary complications of diabetes by decreasing the HbA(1c) level. (c) 2006 Elsevier Ireland Ltd. All rights reserved.