A simplified method to remove and cryopreserve peripheral blood stem cells (PBSC) was utilised to restore the bone marrow in 31 patients with haematological or solid neoplasms after ablative chemotherapy. Mobilization was performed with subcutaneous G-CSF, starting 4 days before the first PBSC harvest and continuing to the last day of harvest. Cryopreservation was carried out by freezing cells to -80 degrees C after addition of autologous fresh plasma with DMSO, in a methanol bath and non-programmed freezer. The PBSC were reinfused in all cases. The mean quantity of CD34 cell (x 10(6)/kg) infused was 6.5 +/- 6.7. The mean number of procedures needed to harvest an appropriate number of PBSC was 3.6 +/- 1.3. The mean times necessary to recover more than 0.5 x 10(9)/l granulocytes were 11 +/- 4 (8-30) days and 23 +/- 13 (8-55) days to obtain more than 20 x 10(9)/l platelets. These results confirm our method as very effective in achieving a high-quality harvest, and it was used in paediatric and adult patients without problems. This procedure, using a non-programmed freezer, simplifies and reduces enormously the cost of the technical measures currently used, enabling their adoption in almost any clinical oncological institution.