Single-agent high-dose melphalan (HDM, 200 mg/m2) has been the most commonly used conditioning regimen prior to autologous stem cell transplant, since its introduction in 1992. We used a more aggressive alkylator-based conditioning regimen in an attempt to overcome early relapse and combat drug resistance. We present a retrospective comparison and long-term follow-up of newly diagnosed patients with multiple myeloma (MM) treated with induction followed by either high-dose carmustine (BCNU) and HDM, or HDM alone, both followed by autologous stem cell transplant (ASCT). Between 1997 and 2002, 104 patients were treated with BCNU/HDM; from 2001 to 2008, 103 patients were treated with HDM alone. Median follow-up of survivors was 78 and 68 months for the BCNU/HDM and HDM groups, respectively. The median PFS was significantly increased with the BCNU/HDM regimen (40.4 vs 20.5 months, P < 0.001). Median overall survival was increased with the BCNU/HDM regimen when compared with HDM alone (88.4 vs 67.2 months, P = 0.07), but the difference was not statistically significant. Transplant-related mortality was similar in both groups (2.9% with BCNU and HDM vs 3.9% with HDM alone). Our findings suggest that the BCNU/HDM preparative regimen should be investigated further and potentially compared in a prospective randomized manner with HDM alone.