In the present study we have used cell culture assays in order to assess the damage in the haematopoietic system 1 year after peripheral blood stem cell transplantation (PBSCT), and to establish at what level, haematopoietic progenitor cells (HPC) or stroma, this damage occurs. Thirty-one patients, nine breast cancer (BC), 17 non-Hodgkin lymphoma (NHL) and five Hodgkin disease (HD), who had received autologous PBSCT were included. Forty-eight normal subjects who had given informed consent were used as controls. Results were also compared with a matched group of patients (25 cases) prior to PBSCT. Progenitor cells were analysed using CFU-GM and plastic adherent delta (Pdelta) assays. Long-term bone marrow cultures (LTBMC) in one and two stages were established. One year after transplant both the number of committed progenitor cells and the CFU-GM production in LTBMC were significantly reduced in the three groups of patients when compared with controls (P < 0.05 or P < 0.01). Two-stage LTBMC experiments showed that the impairment in CFU-GM production was due to damage in both patients' stroma and haematopoietic progenitor cells (HPC). All patients, except those with HD, showed a decreased stromal layer confluence (P < 0.05), with significant differences in cell composition as compared to normal bone marrow (P = 0.001). When all these variables were compared with pretransplant results, we observed that stroma formation was significantly lower after PBSCT (P < 0.05), while the number of progenitor cells analysed by the Pdelta assay was significantly increased (P < 0.05). We can conclude that even 1 year after PBSCT, both the committed HPC and BM stroma remain damaged.