This monograph aims to cover in depth all aspects of bone marrow lymphoid infiltrates, in the context of their wide spectrum of benign, borderline and malignant expressions. As the bone marrow is no longer considered a selective diagnostic procedure in the field of haematopathology and haematology,but a routine need to other subspecialists, we intend to provide a comprehensive treatise for beginners and experienced practitioners alike who deal with patients that are investigated or treated for lymphomas and lymphoid leukemias, manifest with laboratory or clinical signs suspicious for haematological diseases or show features mimicking haematological conditions.