In this research, the regulatory effects of T-lymphocytes on the expansion of hematopoietic cells in human bone marrow were studied. Anti-CD3 McAb and anti-CD8 McAb were used to eliminate the T-lymphocytes in bone marrow MNCs. Cell surface antigens were analysed by flow cytometry. Hematopoietic cells expanded with hematopoietic growth factors (HGFs) in a liquid culture system and the number of CD34(+) cell, CFU-GM and CFU-GEMM were determined. After cultured with HGFs for 20 days the total number of cells expanded by 75.8, 79.6, 77.4 and 67.0 folds respectively in three experimental groups (anti-CD3 McAb, anti-CD8 McAb and anti-CD3 + anti-CD8 McAb) and control group (MNC of bone marrow). The number of CFU-GM in the four groups were 173.67 +/- 18.90, 165.33 +/- 26.58, 170.33 +/- 21.50 and 79.67 +/- 8.33 respectively. The number of CFU-GEMM in the four groups were 431.33 +/- 34.56, 370.33 +/- 42.10, 386.67 +/- 10.02 and 177.67 +/- 26.86 respectively. There were significant differences in the number of CFU-GM and CFU-GEMM between experimental groups and control group. The results showed that the T-lymphocytes in bone marrow could inhibit the expansion of hematopoietic cells in vitro and the formation of CFU-GM and CFU-GEMM. The regulatory mechanism was to be explored.