Myelodysplastic syndromes (MDS) are a group of heterogeneous clonal stem cell diseases with a tendency to progress to leukemic transformation. The cytogenetic and molecular pathogenesis of MDS has not been well understood. SALL4, a newly identified oncogene, modulates stem cell pluripotency and self-renewal capability in embryonic development and also plays a role in leukemogenesis. Overexpression of SALL4 induces MDS-like features and subsequent leukemic progression in transgenic mice. Here, we examined SALL4 expression levels in bone marrow mononuclear cells from MDS patients, acute myeloid leukemia (AML) patients, and normal control subjects using a semiquantitative reverse transcription polymerase chain reaction. Higher levels of SALL4 expression were seen in MDS and AML samples than in control samples. The expression level of SALL4 positively correlated with those of MYC and CCND1, both of which are downstream target genes in the Wnt/beta-catenin pathway. We therefore propose that SALL4 plays a critical role in the pathogenesis of MDS by causing the aberrant activation of the Wnt/beta-catenin pathway.