Six patients with high risk haematological malignancies received peripheral blood progenitor cells (PBPC) from unrelated donors. Four patients received PBPC as primary treatment and 2 following graft failure. Five donors were HLA-A, -B and -DR identical and one had a one antigen mismatch. PBPC were mobilised by treatment with G-CSF for 4-6 days. The patients received a range of 3.4 to 11.4 x 10(8) mononuclear cells/kg and 1.0 to 15.0 x 10(6) CD34 positive cells/kg. Four patients were given Campath 1G and 2 ATG prior to transplantation. The patient with one antigen mismatch received in vitro T-cell depleted PBPC using Campath 1M. All received cyclosporin and 5 in addition methotrexate. All recipients were given G-CSF and all engrafted. The patients developed no or mild acute GVHD. Two patients had limited chronic GVHD of the skin. The recipient of the mismatched graft died from extensive chronic GVHD. Three patients have had a relapse and two are alive and free of leukaemia.