Thirty-three leukaemic patients in CR were treated by high-dose therapy followed by ABMT: 18 of them had acute non-lymphoblastic leukaemia (ANLL) in first remission (CR1) with a mean age of 23.7 years (3-44). All but one of them were conditioned with a polychemotherapy regimen including 6-thioguanine, Ara-C, CCNU, and cyclophosphamide. The marrow cells were purged by chemical means in 16 cases. Five transplant-related deaths were observed: three cardiac failures, one interstitial pneumonitis and one aspergillus pneumonia. At the time of analysis (October 1984), four patients had relapsed and eight were still in unmaintained CR1 (44+, 46+, 30+, and five between 2.5+ and 8+ months post transplant). Fifteen patients had acute lymphoblastic leukaemia: four were autografted in CR1 and 11 children were grafted in CR2; the conditioning regimen was fractionated total body irradiation followed by cyclophosphamide for all but one patient who was conditioned with BACT (Burkitt leukaemia); the marrow was purged by a chemical agent in 11 patients and by monoclonal antibodies and C' in four: four out of 15 patients relapsed (two grafted in CR1 and two grafted in CR2); 10 patients are still in unmaintained CR: two adults grafted in CR1 (26+; 12+ months) and eight children with a mean follow-up of 13.4 months post graft (2 + -45+ months). The clinical study leads to the following conclusions: in adult patients the marrow should be harvested during CR1 and at the time of minimal residual disease. The quality of previous chemotherapy and conditioning regimen prior to ABMT play a prominent role in the in vivo eradication of the leukaemic cells. The real impact of marrow purging is still unknown and a larger series of homogeneous patients, conditioned with the same protocols and the same transplant timing, is required before any conclusions can be drawn.