The prognostic value of bone marrow biopsy was established in 31 patients suffering from stage IIA and IIIA myeloma (Durie and Salmon classification). Data obtained from quantitative marrow cytology permit to differentiate 3 sub-groups of cells: plasmocytes, plasmoblasts, plasmocytes/plasmoblasts of which the incidence on the prognosis and the response to treatment was studied. There is a correlation between the response to MP and the nature of various cells populations and, on the other hand, the type of infiltration. A sub-group of patients, resisting to MP, was identified: diffuse plasmoblastic myelomas of poor prognosis. Induction poly-chemotherapy seems far superior over the MP combination, which was always a controverted issue.