We have reported that serum granulocyte colony-stimulating factor (G-CSF) and interleukin-6 (IL-6) levels rise in patients with chemotherapy-induced myelosuppression. The aim of the present study was to determine whether other cytokines that function at different hematopoietic stages also fluctuate during chemotherapy-induced myelosuppression and whether the extent of cytokine level fluctuations correlate with myelosuppression severity. Fifteen patients participated in the study. Serum levels of stem cell factor (SCF), interleukin (IL)-1 alpha, IL-6, IL-3, granulocyte-macrophage CSF (GM-CSF) and G-CSF were analyzed before chemotherapy and during the myelosuppressive stage and correlations between cytokine levels and myelosuppression severity were examined. The results showed that both serum G-CSF and IL-6 levels rose in patients with chemotherapy-induced myelosuppression. The prechemotherapy serum G-CSF and IL-6 levels correlated well with their respective elevated levels during the myelosuppressive stage. The myelosuppression severity also correlated well with the extent of serum G-CSF level elevation. The serum IL-6 and G-CSF levels during the myelosuppressive stage correlated significantly. Serum SCF levels did not fluctuate significantly during myelosuppression, and IL-1, IL-3 and GM-CSF were rarely detected in serum even after chemotherapy. In the present study, the roles of IL-1 alpha, SCF, IL-3 and GM-CSF chemotherapy-induced myelosuppression were not clear.