The deposition of proteins in the form of amyloid fibrils is the characteristic feature of more than 20 medical conditions affecting the central nervous system or a variety of peripheral tissues. These disorders, which include Alzheimer's disease, the prion diseases and type II diabetes, are of enormous importance in the context of present-day human health and welfare. Extensive research is therefore being carried out to define the molecular details of the mechanism of the pathological conversion of amyloidogenic proteins from their soluble forms into fibrillar structures. This review focuses on recent studies that demonstrate the power of using antibodies or antibody fragments to probe the process of fibril formation, and discusses the emerging potential of these species as diagnostic and therapeutic agents.