In hematopoiesis; the human CD 34 protein is a strict developmental stage-specific antigen that marks hematopoietic stem/progenitor cells, suggesting that it plays an essential role in hematopoiesis. More recently, it has been demonstrated that hematopoietic cells expressing the CD 34 antigen constitute various heterogeneous cell populations in which each CD 34+ subset was associated with commitment to a particular lineage, and differed from other's in reconstituting hematopoiesis. In this report, we have assessed the different functional subpopulation of CD 34+ hematopoietic stem/progenitor enriched from human bone marrow using Isolex TM 50 system according to the strategy on immunomagnetic separation of positive selection. CD 34+ cell population of high purity (> 90% CD 34+) was analyzed by means of double staining procedure of flurorescein conjugated monoclonal antibodies on the two-color FACAcan or FACS 440. Eight cell subsets of at least of bone marrow CD 34 hematopoietic stem/progenitor cells have been defined by undertaking a comparative coexpressing of CD 71, CD45, CD 33 and HLA-DR antigens on CD 34 hematopoietic stem/progenitor cells. The frequencies of various subsets in two illustrative are as following: 1). CD 34+/CD 71- and CD 34+/CD 71+ (23.43%-56.6% versus 33.4%-66.6%): 2). CD 34+/CD45- and CD 34+/CD45+ (80.8%-82.5% versus 8.1%-11.2%): 3). CD 34+/CD 33- and CD 34+/CD 33+ (20.4%-80.6% versus 14.6%-64.8%): 4). CD 34+/DR- and CD 34+/DR+ (6.3%-11.0% verus 82.8%-85.5%). Immunological double color staining of IGSS-APAAP was also used to further analyse the CD 34+ cell subsets as above-mentioned, the results were very similar to those obtained by FACScan. Our data indicate that CD 34+ hematopoietic cell fraction is far from being a uniform cell population, and many works regarding biological properties and regulation mechanism of different subsets of CD 34+ hematopoietic stem/progenitor cells are being carried out.