Nonradioactive colorimetric assay suitable for high-throughput quantification of cell death and cell lysis, based on the measurement of lactate dehydrogenase (LDH) activity released from the cytosol of damaged cells into the supernatant. The Cytotoxicity Detection KitPLUS (LDH) can be performed in a homogeneous format and requires no transfer and centrifugation steps to separate the supernatant from the cells. The color reaction can be stopped for defined assay conditions.