The aim of this study was to evaluate the apoptotic damage to bone marrow cells caused by three chemotherapy regimens for advanced Hodgkin's lymphoma, ABVD, COPPEBVCAD and BEACOPP, which were randomly administered in the HD 2000 GISL trial. Bone marrow mononuclear cells (BMMCs) stained with anti-CD34 antibody and Annexin V, were evaluated by flow cytometry before starting chemotherapy, 30 days after completing chemotherapy and after 6 months. Results are expressed as the percentages of BMMCs positive to anti-CD34, to Annexin V or to both. Fourteen patients treated with ABVD, 11 with COPPEBVCAD and 13 with BEACOPP were evaluated before and 30 days after treatment. Late assessments were made in 6, 7 and 8 of them, respectively. No differences were found among the pretherapeutic flow cytometry findings in relation to the staging characteristics (marrow involvement included). All the regimens increased the apoptotic fraction of the whole mononuclear bone marrow cells (COPPEBVCAD did so significantly) and increased the CD34+ compartment (with significant early differences after ABVD and BEACOPP, tending to late persistence for ABVD, only). All the regimens increased the apoptotic CD34+ cells within the whole BMMC population (significantly after BEACOPP), although with a general trend to decrease in their percentage within the CD34+ compartment over time, even after the most dose-dense regimens. Based on the variations induced in the apoptotic fraction of all mononuclear and CD34+ cells, ABVD was the least toxic regimen and COPPEBVCAD the most toxic one.