CURRENT STATUS The determination of concentration of CD34+ cells is the standard method for evaluation of the quality of a bone marrow graft and of peripheral stem cells. Although the relationship between the dose of CD34+ cells and the speed of graft healing in autologous transplants is a proven fact, it may not always be the case in allogenic transplants. PATIENTS AND METHOD The correlation between the dose of CD34+ cell subpopulations and the speed of healing was monitored in patients indicated for allogenic transplantation of haematopoietic stem cells. The patients were divided according to the type of preparatory regimen they underwent for the purpose of analysis; one group contained those under a myeloablative regimen; a second group contained those under a non-myeloablative regimen. The data was subject to analysis of variance in regression models and non-parametric tests. RESULTS From among the monitored subpopulations, CD34+36+ cells had the greatest effect on the healing process and were the most significant predictor of the speed of healing in patients under a myeloablative regimen. Nevertheless, a dose ofCD34+ cells continued to be the best healing predictor in patients under a non-myeloablative regimen. Also subpopulations of CD34+38+ and CD34+61+ cells had a significant effect on the speed of healing in both groups. CONCLUSION Haematopoietic stem cells and progenitor cells defined by co-expression of specific antigens are likely to play a role, through different mechanisms of action, in the process of healing in patients in different pre-transplant regimens. While the dose of CD34+ cells is still the one which correlates best with the speed of healing in patients who underwent transplantation after non-myeloablative regimen, the dose of CD34+36+ cells appears to be a better predictor for the speed of healing after myeloablative regimens.