Designed to mimic a patient sample, CD-Chex Select contains human leukocytes and erythrocytes in a preservative medium. The cells in CD-Chex Select possess surface and intracellular antigens detectable with fluorescent monoclonal antibodies by flow cytometry. It is a positive procedural flow cytometry control assayed for 11 CD markers used for immunophenotyping: CD26, CD41, CD57, CD58, CD61, CD64, FMC7, TCR α/β, TCR γ/δ, and intracellular CD79a and MPO. CD-Chex Select is designed to represent normal peripheral blood leukocytes where lymphocytes, monocytes, and granulocytes are distinguishable on the basis of light scatter properties. Featuring cap pierceable plastic vials, CD-Chex Select is compatible with automated flow cytometry sample preparation instruments, reducing errors and improving laboratory workflow. It is a positive procedural control designed to monitor reagent staining, erythrocyte lysis, sample preparation, and instrument performance. CD-Chex Select is compatible with BD Biosciences and Beckman Coulter flow cytometry systems.