We analysed the expression of both components of IL-6R, CD126 the ligand binding protein and CD130 the signal transducing protein, on plasma cells from MGUS and multiple myeloma (MM) cases using flow cytometry. CD126 was detectable in 50% of either MGUS or MM patients without any change of expression during disease progression. In contrast, CD130 expression was up-regulated during tumoural expansion (43% of MM patients at diagnosis versus 88% at relapse). Finally, combining CD126 and CD130 expression we found a significant increase of the percentage of CD126+ CD130+ patients at relapse, underlying the crucial role of IL-6 response in the late stage of MM.