Introduction: Cytogenetic changes occur in 50% of patients (pts) with Myelodysplastic Syndromes (MDS). Complex aberrations (cA, = 3 or more) are associated with a very poor outcome. In about 50% of the cases with cA aberrations of the TP53locus are detectable. Those pts show an even worse outcome with a significantly shortened median overall survival (OS) compared to pts with wildtype TP53 (wtTP53). One of the most common cytogenetic aberrations in MDS is an interstitial deletion of the long arm of chromosome 5 (5q). As an isolated aberration, it is associated with a rather favorable prognosis. As part of a cA, 5q deletions however are assumed to even worsen the prognosis further. We wanted to find out in which prevalence 5q deletions and TP53changes appear together and how those two factors in combination or not influence the OS of pts with MDS and cA.