In order to evaluate the importance of genetic alterations in myeloid disorder, we studied the gene structure of the cytokine genes for erythropoietin (EPO), granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3) in 74 patients with myeloid disorders and in 20 healthy volunteers. The cytogenetic results of 54 patients were correlated with the molecular results from Southern Blotting. Concerning the genes for IL-3 and GM-CSF we detected a higher microheterogeneity compared to the genes for EPO and G-CSF. 2 Patients exhibited structural alterations of the IL-3 gene and 2 other patients showed transient alterations of the G-CSF gene. We conclude, that there are no clear disease-associated cytogenetic and molecular alterations, structural alterations seem to be rare events.