The “Bologna 96” clinical trial was designed in an attempt to prospectively compare a single autologous transplantation (Tx-1) versus double autologous transplantation (Tx-2) as part of first-line therapy for patients with symptomatic multiple myeloma (MM) and less than 60 years of age. Tx-1 was given to support melphalan 200 mg/m2 (MEL-200); Tx-2 was given to support a first course of MEL-200 followed, within 3 to 6 months, by melphalan 120 mg/m2 + busulfan 12 mg/kg. In both arms of the study, autologous transplantation was preceded by 4 courses of VAD and subsequent collection of peripheral blood stem cells with high-dose cyclophosphamide 7 g/m2. An analysis was performed using an intent-to-treat approach on 228 patients who were randomly assigned to Tx-1 (n=115 patients, median follow-up of living patients: 45 months) or Tx-2 (n=113 patients, median follow-up of living patients: 54 months). In comparison with Tx-1, Tx-2 prolonged event-free survival (EFS) of 12 months (P=0.001) and time to progression (TTP) of 17 months (P=0.0001). Six-year projected probability of survival (OS) was 44% for Tx-1 and 63% for Tx-2 (P=0.3). The probability of attaining stringently defined complete remission (CR) or near complete remission (nCR) was 35% for Tx-1 and 48% for Tx-2; the sample size analyzed was not powered to detect a statistically significant difference between the two groups. Among patients randomized to Tx-1, attainment of CR or nCR was an essential prerequisite for extended OS (P=0.0001), EFS (P=0.000002) and TTP (P=0.000007). At the opposite, the benefits of double autologous transplantation were the greatest among patients who failed at least nCR. In particular, patients who did not attain CR or nCR after the first autologous transplantation and by study randomization received a second transplantation had a significantly longer duration of OS (P=0.01), EFS (P=0.000006) and TTP (P=0.000001) than patients who had the same response status but were assigned to receive a single autologous transplantation. Compared to Tx-1, Tx-2 significantly extended OS (P=0.04), EFS (P=0.000006) and TTP (P=0.000001) also among patients who failed Cr or nCR after receiving the entire treatment program to whom they were assigned (Tx-1 or Tx-2). At the opposite, for patients who were in CR or nCR after the first transplantation, there was no significant benefit from receiving a second autologous transplantation. In conclusion, data from the present analysis show that in comparison with a single autologous transplantation, i) double transplantation significantly prolonged EFS and TTP among younger (< 60 years) patients with previously untreated MM; ii) double autologous transplantation was of particular benefit for patients who failed at least nCR. Mature data derived from the final analysis of the study must be awaited before definite conclusions can be given concerning the impact of double autologous transplantation on the outcome of patients with MM. Supported by Università di Bologna, Progetti di Ricerca ex-60% (M.Cavo); Ministero dell’Università e Ricerca Scientifica, progetto FIRB, RBAU012E9A_001 (M. Cavo); and Fondazione Carisbo.