Myelodysplastic syndrome Working Group of the Croatian Cooperative Group for Hematologic Diseases (CROHEM), Referral center of the Ministry of Health of the Republic of Croatia for diagnostics and treatment of MDS, as well as the Croatian Society for Haematology of the Croatian Medical Association have made Croatian guidelines for diagnosis and treatment of myelodysplastic syndrome (MDS). MDS is a heterogeneous group of clonal hematopoietic stem cell disorders characterized by ineffective hematopoiesis, dysplasia, cytopenia and risk of transformation to acute myeloid leukemia (AML). Diagnosis is based on morphological characteristics of hematopoietic cells supplemented with the cytogenetic analysis and bone marrow flow cytometry. Due to great differences in the natural course of the disease, i.e. time to progression to AML and the expected time of survival several scoring systems have been developed to determine the disease risk. The treatment of patients with MDS is based on the risk factors of the disease as well as the individual risk of treatment.