Abstract: Objective To evaluate the cytogenetic characteristics of the patients with acute myelomonocytic leukemia (AML-M4), acute monocytic leukemia (AML-M5) and myelodysplastic syndrome (MDS).Methods Chromosomes of bone marrow cells were prepared by short-term culture.Karyotype analysis was performed in 100 AML-M4,46 AML-M5 and 115 MDS by R-banding technique.Results 26 % (26/100) AML-M4 had clonal cytogenetic abnormalities which mainly include +8,t(8;21) and -7.26 % (12/46) AML-M5 had clonal cytogenetic abnormalities which mainly include +11. 39 % (45/115) had clonal cytogenetic abnormalities which mainly include +8, Hypodiploid and -7. Conclusion Cytogenetic detection is very important for the diagnosis of myelodysplastic syndrome and acute myelocytic leukemia.