The system performance of an antibody-functionalized microchamber array, developed for selectively binding target cancer cells, is quantitatively characterized. The devices are designed to allow accurate counting of loaded and captured cells from heterogeneous suspensions. Specific interaction between cancer cell receptors and immobilized surface ligands has been demonstrated under static conditions. Performance measures such as specificity, sensitivity and accuracy are uniquely defined and experimentally evaluated. Several cell mixtures have been tested, and the quantitative system performance criteria are reported as a function of cell concentrations in the tested suspensions. These criteria provide a critical quantitative basis for a comparison among different systems aimed at selectively isolating target bio-species from complex mixtures.