The NK Cell Isolation Kit was developed for the isolation of untouched NK cells from single-cell suspensions of murine spleen. Non-NK cells, i.e. T cells, dendritic cells, B cells, granulocytes, macrophages, and erythroid cells are magnetically labeled by using a cocktail of biotin-conjugated antibodies and Anti-Biotin MicroBeads. Isolation of highly pure unlabeled NK cells is achieved by depletion of non-target cells. The kit has been optimized to give outstanding purities in C57BL/6J mice.