The purpose of this study was to evaluate the efficiency and safety of tandem double autologous peripheral blood stem cell transplants (T-APBSCT) for de novo multiple myeloma (MM) patients. The clinical data of 3 patients treated by T-APBSCT after chemotherapy were analyzed retrospectively. The first mobilization regimen was cyclophosphamide (CTX) combined with G-CSF 5 microg/(kg x d) and the conditioning regimen for the transplantation was 180 mg/m(2) melphalan. The second mobilization regimen was CTX and VP16 in combination with G-CSF 5 microg/(kg x d) and the conditioning regimen for the transplantation was 180 mg/m(2) melphalan or 10 Gy total body irradiation plus 140 mg/m(2) melphalan. The interval of two in tandem autotransplants was 31, 15 and 27 weeks. For two in tandem APBSCT in 3 patients, the cell number of mononuclear cells (MNCs) transfused was 4.7 x 10(8), 2.798 x 10(8), 6.08 x 10(8)/kg and 1.67 x 10(8), 2.798 x 10(8), 4.28 x 10(8)/kg, while the dose for CD34(+) cells were 3.25 x 10(6), 9.6 x 10(6), 5.91 x 10(6)/kg and 6.9 x 10(6), 9.6 x 10(6), 5.91 x 10(6)/kg for their first and second transplants respectively. The results showed that all patients gained prompt and sustained hematopoietic reconstitution. In double tandem transplantation for 3 patients the interval of absolute neutrophil count (ANC) >or= 1 x 10(9)/L were at day 12, 0, 10 and 12, 25, 0; while platelet count >or= 20 x 10(9)/L were at day 12, 0, 10, and 11, 25, 20 days. The median follow-up time for 2 T-APBSCT was 44 (range 19 - 58) months. Two patients survived, one of them was in complete remission and other was in a stable PR stage, but one out 3 patients died at 58 months after T-APBSCT. It is concluded that the method of T-APBSCT for de novo multiple myeloma is probably safe and effective.