Assaying enzyme-catalyzed transformations in high-throughput is crucial to enzyme discovery, enzyme engineering and the drug discovery process. In enzyme assays, catalytic activity is detected using labelled substrates or indirect sensor systems that produce a detectable spectroscopic signal upon reaction. Recent advances in the development of high-throughput enzyme assays have identified new labels and chromophores to detect a wide range of enzymes activities. Enzyme activity profiling and fingerprinting have also been used as tools for identification and classification, while microarray formats have been devised to increase throughput.