The SIRT1 Inhibitor/Activator Screening Kit provides a fast, convenient, sensitive, and reliable test, which is suitable for high-throughput screening of SIRT1 inhibitors/activators. An inhibitor control (nicotinamide) is included to compare the efficacy of the test inhibitors. In this assay, Sirtuin 1 also deacetylates a fluorescently labeled substrate, followed by cleavage of the deacetylated substrate to release the fluorescent group, which is detected at Ex/Em = 400/505 nm using a fluorometer or fluorescence multiwell plate reader. In the presence of a SIRT1 inhibitor, deacetylation is impeded, preventing cleavage of the substrate and release of the fluorescent group. A SIRT1 activator however enhances SIRT1 activity resulting in a higher fluorescent signal in comparison to the control.