AbstractRecombinant human granulocyte colony‐stimulating factor (rhG‐CSF) and erythropoietin (rhEPO) were used to treat patients with aplastic anemia (AA). In terms of effects on erythrocyte recovery, the combined use of rhG‐CSF and rhEPO showed a favorable response in 6 of 14 (42.9%) patients with moderate AA following 10 weeks treatment and in 3 of 14 (21.4%) patients thereafter. However, the response was poor in patients with severe AA (3/13). A favorable response in severe AA was observed in 1 of 13 (7.7%) patients following 10 weeks treatment and in 2 of 13 (15.4%) patients thereafter. The overall effect on erythrocytes was observed in 44.4% patients. A dose of 400 μ/m2G‐CSF was sufficient to cause an increase in neutrophil count and 100 IU/kg rhEPO appeared to be sufficient to cause an increase in erythrocyte count. In 6 of 27 (22.2%) patients, a trilineage response was observed. Interestingly, a delayed and long‐lasting effect was obtained in 5 of 27 (18.5%) patients. These results suggest that rhG‐CSF can synergize with rhEPO in erythrocyte response, especially in patients with