To evaluate the effects of rhG-CSF and rhSCF on mobilization of the peripheral blood stem cells, 15 monkeys were divided into control, rhG-CSF 10 micro g/(kg x day) and rhG-CSF 10 micro g/(kg x day) + rhSCF 50 micro g/(kg x day) treated groups. Monkeys were administered with vehicle, rhG-CSF and rhG-CSF + rhSCF subcutaneously once daily for 14 days, respectively. The results showed that the highest counts of leukocyte of rhG-CSF treated group were 411% of baseline value on day 7 after administration, compared with that of rhG-CSF + rhSCF treated group which were 538% on day 9. The highest counts of leukocytes lasted for 3 days in combined treated group. CFU-GM from peripheral blood in the two groups were 8.37 and 11.75 times higher at 5 and 9 days respectively after the mobilization. It is concluded that rhG-CSF significantly increases the number of peripheral blood leukocytes and CFU-GM, and a better effect can be obtained by rhSCF + rhG-CSF combined administration.