Enzo’s panel of fluorescence-based live cell assays are designed to assess the impact of toxic agents on overall cell function, with particular emphasis on the plasma membrane, lysosomal, mitochondrial and nuclear compartments. Many of the assays have been optimized for analysis by flow cytometry, while others are geared towards microplate-based cytometry. Early secondary screening of candidate drugs for potentially adverse cell activity in the drug discovery phase could predict later risks in drug development arising from drug safety issues. Such a screening approach can aid in selecting the best candidate compounds for further drug development efforts, as well as provide preliminary benchmarking of dosing limits in preclinical toxicity studies. The highlighted portfolio of assays should provide an early indication of compounds that represent potential hazards towards human health and the environment.