For in vitro studies, both CD34+ selected cell and mononuclear cell (MNC) can be used to expand hematopoietic stem/progenitor cells. To investigate the expansion characteristics of mononuclear cells (MNC) and CD34+ selected cells the two cell fractions were cultured in the medium containing cytokine cocktails of SCF + IL-3 + IL-6 + FL + Tpo. It was found that the CD34+ selected cells had presented a high proliferation potential. The expansion of CD34+ selected cells could be maintained for 8 weeks while that of MNCs declined after 4 weeks. During the culture period, the maximum expansion of total cells in CD34+ selected cell culture achieved 31,270.9 +/- 8640.5 times, while that of MNC reached 50.9 +/- 8.2 times only. In the culture of MNCs, the colony density and the proportion of CD34+ cells increased from day 0 to day 7. However, in the culture of CD34+ selected cells, both the colony density and the proportion of CD34+ cells declined continuously during the whole culture period. During the ex vivo culture of CD34+ selected cells, the maximum expansion of CFU-GM and CD34+ cells achieved 185.7 +/- 14.1 fold and 191.7 +/- 188.8 fold, respectively. They are much higher than that of MNC, which were 12.4 +/- 3.2 fold and 50.6 +/- 33.2 fold only. While the BFU-E of both cell fractions only expanded by few times, which were 7.2 +/- 5.2 and 10.1 +/- 3.4 times, respectively. The results showed that the CD34+ selected cells culture could obtain more CFU-GM cells and CD34+ cells during the whole culture period.