The main purpose of VIDAZA® DUE (Drug Use Examination) is to collect and evaluate the safety information of Korean MDS patients treated with VIDAZA®(SC or IV) according to the approved package insert, after approval of marketing authorization for new drug in Korea. In addition, the efficacy information of VIDAZA® in clinical practice is collected and evaluated. This DUE is a prospective, multi-centre, observational, non-interventional, post-marketing surveillance. At least 600 patients' data that is eligible for safety assessment will be collected.