In order to explore the role of real-time PCR in detecting minimal residual disease in multiple myeloma and Waldenstrom's macroglobulinemia after autologous peripheral blood stem cell transplantation (APBSCT), real-time PCR was used to quantitate the IgH rearrangement in 8 patients with multiple myeloma (MM) and 1 case of Waldenstrom's macroglobulinemia before and after APBSCT. The results showed that the copies of IgH rearrangement pre- or post-APBSCT were 3108 +/- 1043 and 549 +/- 660 (P < 0.05) respectively. The number of IgH copies was positively correlated with the amount of plasmocytes in patient 's bone marrow and the M-protein in peripheral blood (r = 0.86, P < 0.05). Similar result was obtained in a case of relapsed Waldenstrom's macroglobulinemia. In conclusion, the quantitative analysis of IgH rearrangement by real-time PCR is a novel way to evaluate the therapeutic efficaciousness and predict the prognoses in MM patients.