Although outcome in multiple myeloma (MM) patients has improved significantly with the introduction of autotransplants (AT), the curability of this approach remained to be demonstrated. Therefore, we analysed outcome and prognostic factors using a logistic regression model in 515 consecutive newly diagnosed and previously treated patients intended to receive melphalan-based tandem transplants with follow up of > or = 5 years. One quarter of patients had event-free survivals (EFS) > or = 5 years with no further relapses seen after 7 years (46 patients on plateau). On multivariate analysis, factors associated with EFS > or = 5 years were absence of chromosome 11 and 13 abnormalities (odds ratio: 6.1), < or = 12 months of preceding standard-dose therapy (SDT) (OR: 2.6) and beta-2 microglobulin (B2M) level < or = 2.5 mg/l at time of first AT (OR: 1.7). Patients with only favourable variables (25%) had a 7-year EFS in excess of 35%, compared with 15% and 10%, respectively, with one (43%) or two unfavourable variables (27%), and 0% for 5% of patients with three unfavourable variables (P < 0.0001). Using a 1-year landmark analysis to allow for guaranteed time and thereby excluding early treatment failures, attaining a complete remission (CR) had no significant effect on long-term survival. Our data are consistent with cure in MM patients with a CR duration . or = 7 years and re-establishment of a monoclonal gammopathy of undetermined significance (MGUS) phase in those with persistent evidence of disease post transplantation, but without disease progression > or = 7 years.