CD34+ progenitor cells were harvested from bone marrow and peripheral blood from 10 healthy donors by immunomagnetic isolation and enrichment procedures. The CD34+ cell population was investigated using a battery of enzyme reactions and monoclonal antibodies on cytospin preparations. Additionally, morphometric measurements were carried out and also liquid suspension culture studies were performed to ascertain vitality and stem cell character. More than 95% of the total yield of medullary CD34 progenitors expressed CD45 (LCA), CD43 (MT1) and Β-glucuronidase. Reactivity with CD33 (My9), CD15 (LeuMl), CD38 (Leul7), CD20 (L26) and Ret40f (glyco-phorin C) was assumed to be in keeping with a transition into more differentiated elements of the various hemopoietic lineages. Morphometric analysis revealed conspicuous heterogeneity of the CD34+ cell population considering size measurements. This finding was in line with the diversities of antigen expression, indicating the more committed nature of CD34+ stem cells derived from the bone marrow in comparison with those progenitors isolated from the peripheral blood. Moreover, proliferation marker staining by PCNA disclosed a positivity in a considerable number of progenitors in contrast to the findings in CD34+ cells that are found in the peripheral blood.