Multiple myeloma (MM) is a currently incurable disease caused by the proliferation of malignant plasma cells. Although the pathogenesis of the disease still remains unclear, recent research in the biology of MM has produced new insights into the factors that control the growth and survival of myeloma cells. Among the growth factors, interleukin-6 (IL-6) has an essential role. Evidence suggests that IL-6 is not only a growth factor, but also a survival factor in MM, inhibiting apoptosis in myeloma cells. IL-6 interacts with several factors which are involved in the pathogenesis of MM, such as adhesion molecules, tumour suppressor genes and oncogenes. Considering the essential role of IL-6, it could serve as a target for new therapeutic interventions. Neutralizing the effect of IL-6 may result in a regression of tumour progression.