INTRODUCTION: An increased incidence of autoimmune diseases has been reported in patients with myelodysplastic syndrome (MDS). The aim of the present study was to determine whether this association includes Danish MDS-patients. A possible association between autoimmune comorbidity and French-American-British Classification of Myelodysplastic Syndrome (FAB) or karyotype was also investigated. MATERIAL AND METHODS: The study is based on retrospective examination of medical records. The patients included in this study were identified by a search in Fyns Amts Sygehusvaesens Patientregister. Patients diagnosed with MDS from 2001 to 2005 were included. The search resulted in inclusion of 64 patients. On the basis of their autoimmune status, patients were divided into two groups: One group with MDS and autoimmune comorbidity and one group with only MDS. The two groups were compared by non-parametric statistics. RESULTS: There was a significantly increased incidence of autoimmune disease in patients with MDS. It was not possible to demonstrate an association between autoimmune comorbidity and age, sex, FAB- or karyotype. CONCLUSION: The present study shows an increased incidence of autoimmune disease among Danish patients with MDS which is in accordance with the majority of previous studies on this issue. Data suggests that treatment of autoimmune comorbidity may also improve some of the clinical and biochemical features of MDS.