['The purpose of this study was to investigate whether purified CD34(+) cells from first-trimester fetal blood are a source of primitive and committed hemopoietic progenitors.', 'CD34(+) cells from first-trimester fetal blood and term cord blood were assayed for committed hemopoietic progenitor cells, high proliferative potential colony-forming cells, and long-term culture-initiating cells.', 'First-trimester CD34(+) cells that were compared with cells at term generated fewer hemopoietic progenitor cells and fewer high proliferative potential colony-forming cells with lower recloning efficiency(P <.001). First-trimester CD34(+) cells tended to contain more long-term culture-initiating cells, both in bulk cultures and by limiting dilution analysis. The ratio between committed and primitive progenitors was 3 in the first-trimester and 20 in the term cord blood, respectively.'] Do cD34+ cells from first-trimester fetal blood are enriched in primitive hemopoietic progenitors?