More than 20 diseases have been identified which are caused by the deposition of amyloid. Natural and chemically synthesized amyloidogenic proteins are used widely to study the structure, assembly,and physiologic effects of both oligomeric and fibrillar forms of these proteins. In many cases,conflicting results arise in these studies,in part owing to difficulties in reproducibly preparing amyloidogenic proteins in a well-defined assembly state.To avoid these problems, several methods have been devised that provide reliable means of preparing amyloid-forming proteins for experimental use.Here,we discuss methods that have been used successfully to prepare one such protein,the amyloid #x03B2; protein (Aβ,involved in Alzheimer's disease.