Engraftment was achieved in 43/45 (95%) recipients of peripheral blood stem cells (PBSC) from HLA-compatible unrelated donors (n = 45), compared to all 45 patients in matched controls receiving bone marrow and 14/18 (78%) recipients of CD34-selected PBSC (P < 0.01). The time to reach ANC >0.5 x 10(9)/l was a median of 16 days in the PBSC and CD34 groups, compared to 20 days in the bone marrow controls (P < 0.001 vs PBSC). The time to reach platelets >50 x 10(9)/l was a median of 23 days in the PBSC group and 24 days in the CD34 group, which was significantly faster than 29 days in the bone marrow controls (P < 0.01). Acute GVHD grades II-IV developed in 30% in the PBSC group, 20% in the recipients of bone marrow and 18% in the CD34 group. The corresponding figures for chronic GVHD were 59%, 85% and 0% (P < 0.01) in the three groups, respectively. The probability of non-relapse death was 27% in the recipients of PBSC, 21% in the bone marrow controls and 60% in the CD34 group (NS). The 2-year leukaemia-free survival was 46% in the PBSC group, 41% in the bone marrow group and 25% in the CD34 group (NS).