To compare the clonogenicity and distribution of CD34⁺ subsets in bone marrow (BM), granulocyte colony-stimulating factor (G-CSF) mobilized peripheral blood (PB) and cord blood (CB), we analyzed in vitro colony formation and CD34⁺ cells co-expressing differentiation molecules (CD38, HLA-DR), myeloid associated molecules (CD13, CD33), a T-cell associated molecule (CD3), and a B-cell associated molecule (CD19) from mononuclear cells (MNCs) in the three compartments. The proportions of CD34⁺CD38^- cells (BM: 4.4±2.8%, PB: 5.3±2.1%, CB: 5.9±3.9%) and CD34⁺HLA-DR^- cells (BM: 4.7±3.4%, PB: 5.5±2.3%, CB: 6.1±3.7%) did not differ significantly among the compartments. In contrast, a significantly higher proportion of CD34 cells of PB and CB co-expressed CD13 (75.0±11.4%, 77.7±17.3%) and CD33 (67.1 ±5.7%, 56.8±10.3%) compared with those of BM (43.0±6.3%, 27.6±5.1%) and a significantly higher number of granulocyte-macrophage colony-forming units (CFU-GM) and erythroid burst-forming units (BFU-E) were detected in MNCs derived from PB and CB compared with those from BM (p<0.01). The proportion of CD34⁺CD19⁺ cells was higher in BM (34.9±11.9%) than those in PB (5.6±3.0%)and CB (4.7=2.1%) (p<0.05). The proportion of CD34⁺CD3⁺ was comparable in all three compartments. In conclusion, our findings show that MNCs of mobilized PB and CB display similar phenotypic profiles of CD34⁺ subsets and clonogenicity, different from those of BM.