The bone marrow is the site of hematopoesis and contains mixed population of blood cells including erythrocytes, granulocytes, monocytes, dendritic cells, lymphocytes and hematopoietic stem cells. The following protocol provides a simple and fast method for isolation of bone marrow immune cells (no erythrocytes) from mouse femurs with a yield of approximate 8 × 107 cells in 5 ml culture media (1.6 × 104 cells/μl). Further isolation or flow cytometric analysis might be required for study of specific immune cell types.