Cayman's HDAC1 Inhibitor Screening Assay provides a fast, fluorescence based method for screening HDAC1 inhibitors. The procedure requires only two easy steps, both performed in the same microplate. The fluorescent reaction product is analyzed using excitation wavelengths between 340-360 nm and emission wavelengths between 440-465 nm. Sufficient purified HDAC1 is provided for 100 tests.