The Medicines and Healthcare Products Regulatory Agency (MHRA) 1 article published in JoVE Medicine Reproducibility and Harmonization in Research Using Biological Standards: The Example of Platelet Agonist Collagen-Related Peptide Carmen H. Coxon1, Peter Rigsby1 1Medicines and Healthcare products Regulatory Agency Here we present a method to standardize the platelet agonist collagen-related peptide cross-linked (CRP-XL) using light transmission aggregometry. While the protocol is targeted at platelet function, the experimental process can be applied to most biological molecules and bioassays to ensure scientific rigor and reproducibility.