Aggregation of the â-cell product islet amyloid polypeptide (IAPP) is believed to be an important event in the development of the â-cell lesion in type 2 diabetes. Preamyloidotic oligomeric IAPP assemblies exert toxic effects on â cells that die, leading to reduced â-cell mass. Normal human islets, when isolated and cultured in vitro or transplanted into nude mice, also develop amyloid deposits, which are associated with increased â-cell death and reduced â-cell mass. The possible role of IAPP aggregation and amyloid formation in loss of islet transplant function should be taken into consideration and studied further.