Induction of heme oxygenase-1 (HO-1) expression in recipients of allogeneic islets can lead to long-term survival (>100 days) of those islets. We tested whether administration of bilirubin would substitute for the beneficial effects of HO-1 expression in islet transplantation. Administering bilirubin to the recipient (B6AF1) or incubating islets in a bilirubin-containing solution ex vivo led to long-term survival of allogeneic islets in a significant percentage of cases. In addition, administering bilirubin to only the donor frequently led to long-term survival of DBA/2 islets in B6AF1 recipients and significantly prolonged graft survival of BALB/c islets in C57BL/6 recipients. Donor treatment with bilirubin up-regulated mRNA expression of protective genes such as HO-1 and bcl-2 and suppressed pro-inflammatory and pro-apoptotic genes including monocyte chemoattractant protein-1 (MCP-1), caspase 3 and 8 in the islet grafts before transplantation. Furthermore, treatment of only the donor suppressed the expression of pro-inflammatory cytokines including tumor necrosis factor- (TNF-), inducible nitric oxide synthase (iNOS), MCP-1 and other pro-apoptotic and pro-inflammatory genes normally seen in the islets after transplantation. Donor treatment also reduced the number of macrophages that infiltrated the islet grafts in the recipients. Pre-incubation of TC3 cells with bilirubin also protected the cells from lipid peroxidation. Our data suggests that the potent anti-oxidant and anti-inflammatory actions of bilirubin may contribute to islet survival.