In this retrospective multicentre study, we analysed the results of 82 consecutive second early allogeneic transplants for primary (n = 28) or secondary ([n = 54) graft failures performed between 1985 and 1997 in patients with acute leukaemia (n = 33), aplastic anaemia (n = 29) or chronic myeloid leukaemia (n = 20). HLA-matched siblings were used in 64 cases. The same donors were used for both transplants in 56 cases and the first transplant was T-cell depleted in 30 cases. The median age at transplant was 25 years and the median intertransplant time interval was 2 months. Estimates of the 3-year overall survival and day 100 transplant-related mortality were 30% and 53% respectively. A recipient age < 34 years at transplant, an intertransplant time interval > or = 80 d and a positive recipient cytomegalovirus serology were predictors of a better outcome. The use of cyclosporin A (CsA) after second transplant had a dramatic impact on outcome, the best results being observed with CsA alone. The day 40 probability of neutrophil recovery was 73%. The use of peripheral blood progenitor cells (PBPCs) was associated with a higher and faster neutrophil recovery. Other factors associated with neutrophil recovery were an intertransplant time interval > or = 80 d and a positive recipient cytomegalovirus serology. Therefore, second early allogeneic transplantation for graft failure is an effective treatment, especially if patients can receive CsA for graft-versus-host disease prevention and are retransplanted more than 80 d from first transplant.