Alzheimer's disease is thought to be triggered by production of the amyloid beta (Abeta) peptide through proteolytic cleavage of the amyloid precursor protein (APP). The binding of Cu2+ to the copper-binding domain (CuBD) of APP reduces the production of Abeta in cell-culture and animal studies. It is expected that structural studies of the CuBD will lead to a better understanding of how copper binding causes Abeta depletion and will define a potential drug target. The crystallization of CuBD in two different forms suitable for structure determination is reported here.