This proposal aims use a novel approach whereby deuterated amyloid peptide fibrils are givenhydrogenated growing ends, and analysed using SANS. The data will enable us to measureindependently both fibril length and linear growth rates for amyloid fibrils. This cannot be doneusing current biophysical techniques, which only probe the rates of conversion of overall %peptide in non-fibrillar to fibrillar form; our proposed experiments absolutely depend on the ability to exploit the contrast between hydrogenated and deuterated peptides that neutron scattering allows. Linear growth rate information is key to understanding the physico-chemical and biological properties of amyloid fibrils, in processes ranging from prion disease propagation, to self-assembly of artificial peptide nano-fibers, and our method will greatly enhance research in the field.