The aim of this study is to give a current view of the importance of evaluating preparations of smears of bone marrow (BM) aspirates in the diagnosing and monitoring the course of multiple myeloma (MM). Special attention is given to the indication and technique of aspiration biopsy, diagnostic and differential-diagnostic importance of evaluating the percentage representation of plasmatic cells in the bone marrow and their morphological deviation from the point of view of distinguishing them from reactive plasmocytosis and monoclonal gammopathy of undetermined significance. Also addressed is the issue of selected morphological classification systems including their benefits in identifying and forecasting the prognosis for the disease. A large part of the report is dedicated to the interpretational limitations of evaluating BM smear samples for the diagnosis and monitoring of the course of MM, and due attention is also given to indication for and assessment of the importance of histological examination of a BM trepanobioptic sample of bone marrow and the benefits of particular specialized methods, especially the examination of immunophenotypic, proliferative and apoptotic qualities of plasmocytes. The report shows that quantitative and cytomorphological evaluation of bone marrow samples still forms integral part of the standard algorithm of methods used in MM diagnosing and monitoring, and requires an extremely qualified approach to BM collection, the preparation of the smear and to precise evaluation, as well from the point of view of clinical interpretation.