Beta-amyloid (Aβ) peptides derived from amyloid precursor protein are found in human cerebrospinal fluid (CSF) and have proven to be informative biomarkers with respect to neurodegeneration, especially Alzheimer’s disease (AD). Quantification of A&beta peptides has proven useful in discriminating AD from other dementias and in staging AD patients with respect to the natural progression of the disease. The Aβ38 Peptide (4G8) Kit provides a sensitive and efficient means to monitor changes in concentrations of Aβ38 peptide and has been validated for measurement in human CSF and mouse plasma. This assay is also compatible with other sample types, including conditioned neuronal cell culture medium, cell lysates, and tissue homogenates such as mouse brain. The kit was developed according to “fit for purpose” principles and is consistent with guidance from the Clinical and Laboratory Standards Institute. This validated assay uses an Aβ38-specific capture antibody with an anti-beta amyloid (17-24) antibody (4G8 clone) as the detection antibody. The 4G8 clone is provided by Covance Research Products, Inc.