A monosomal karyotype (MK), defined as ≥2 autosomal monosomies or a single monosomy in the presenceof additional structural abnormalities, was recently identified as an independent prognostic factor conveying anextremely poor prognosis in patients with acute myeloid leukemia (AML). In the present study, after excludingpatients with t(15;17), t(8;21), inv(16) and normal karyotypes, 324 AML patients with cytogenetic abnormalitieswere the main subject of analysis. The incidences of MK were 13% in patients aged 15 to 60 years and 18% inthose between 15 and 88 years old. MK was much more prevalent among elderly patients (p < 0.001) and wassignificantly associated with the presence of -7, -5, del(5q), abn12p, abn17p, -18 or 18q-, -20 or 20q- and CK (forall p < 0.001 except for abn12p p=0.009), and +8 or +8q was less frequent in MK+ AML(p=0.007). No correlationwas noted between monosomal karyotype and FAB subtype (p > 0.05); MK remained significantly associatedwith worse overall survival among patients with complex karyotype (p= 0.032); A single autosomal monosomycontributed an additional negative effect in OS of patients with structural cytogenetic abnormalities (P=0.008).This report presents the prevalence, feature and prognostic impact of MK among a large series of Chinese AMLpatients from a single center for the first time.