Antibody-dependent cell-mediated cytotoxicity (ADCC) is the mechanism by which many Class I therapeutic antibodies, including rituximab and trastuzumab, achieve clinical effi cacy. In particular, molecules based on IgG1 isotype may be expected to elicit ADCC and it is recommended that developers assess an antibody’s potential to elicit ADCC throughout the development process. Current ADCC assay techniques, such as chromium or calcein release assays, suffer from drawbacks like cellular “leakiness” leading to high background and variability, or lack of specifi city for target cell killing (such as LDH release). We present a robust assay format using our proprietary enzyme fragment complementation (EFC) technology that specifically measures killing of target cells in a dye-free & radioactivity-free assay. These assays have very low background, thus producing robust assay windows, with excellent precision. Importantly, the same assay can be used for both ADCC and CDC, as well as other cell death mechanisms. Examples of rituximab-, cetuximab- and trastuzumab-mediated ADCC in multiple cancer cell models, with the use of primary NK cells and PBMCs, will be presented.