High dose chemotherapy with autologous stem cell transplantation (ASCT) improves outcomes in patients 65 years of age or less with multiple myeloma. Survival and costs in a cohort of 16 patients who received melphalan and prednisone as part of a clinical trial were compared with those of 36 patients referred to our centre for consideration of ASCT. In the transplant group, survival and costs were extrapolated to match the period of observation in the melphalan and prednisone group. Patient-specific and average costs were calculated from the perspective of the Ontario Ministry of Health. Costs and survival were varied by 50% in the sensitivity analysis. Transplantation improved life expectancy by 19.3 months with a cost difference of 30,517 Canadian dollars. The incremental cost-effectiveness of transplantation compared with melphalan and prednisone was 25,710 Canadian dollars per life-year gained when additional pamidronate and follow-up costs were considered. Discounting costs and survival at 3 and 5% did not result in important differences. The sensitivity analysis resulted in best and worse case scenarios for transplantation compared with melphalan and prednisone of 13,049 dollars and 63,954 dollars per life-year gained respectively. In comparison with melphalan and prednisone, ASCT appears to be cost-effective in patients 65 years old or younger with myeloma.