A high percentage of islets fail to survive intraportal transplantation, but the absolute amount and time course of this loss are uncertain. We have devised a technique to directly quantitate the number of surviving islets using simultaneous selective transplantation of islets and inert beads into the posterior lobes of the liver. Islet:bead ratio did not change significantly within the first 2 hours, but fell progressively thereafter, giving calculated islet survival rates of 89, 43, and 66% at days 1, 7 and 28, respectively. This technique provides a baseline from which to develop strategies to improve the survival of intraportally transplanted islets.