A series of cytokines, like IL-3, IL-5, IL-6, IL-10, M oncostatin, ILGF1, stimulate the growth of myelomatous cells. Some of them can worsen the prognosis of patients with multiple myeloma through their negative effects (osteolysis, inhibition of erythropoiesis) or may induce benefic effects (megakariopoiesis stimulation). The presence of chromosomal abnormalities might add to a positive prognosis (hyperdiploidia of 3, 5, 7, 9, 11, 15, 19, 21) or, conversely, could be a bad prognostic factor: t(4;14), t(14;16), del 13q and 17p13. The study of gene expression in multiple myeloma represents a modern method of identifying the genes which, through their overexpression, aggravate the patients 'prognosis. Until now, approximately 33000 types of these genes have been studied in multiple myeloma.