SNF2 family includes proteins essential to genome replication, repair, and expression. The cDNA cloning and initial characterization of a novel mouse member of this protein family was reported, and the new member was designated as Ercc6l (excision repair cross-complementing rodent repair deficiency, complementation group 6-like) by MGNC. The cDNA of Ercc6l was 4 002 bp and firstly cloned in silico and then identified by RT-PCR in mouse embryo heart. This gene was composed of 2 extrons and mapped to mouse chromosome X. The longest ORF encoded a putative protein of 1240 amino acids. Eight highly conserved sequence regions of SNF2 protein were present in the deduced protein. Alignment against members of SNF2 family initially placed Ercc6l into ERCC6 subfamily of SNF2 family. EGFP-tagged Ercc6l protein was localized in cytoplasm of HeLa, NIH3T3 and B16 cells. BLAST search in EST database retrieved 69 homologous ESTs of Ercc6l, most of which were from mouse embryonic and tumorous tissues. RT-PCR performed on a panel of different mouse tissues demonstrated that Ercc6l strongly expressed in mouse embryo but significantly downregulated in neonate and adult normal tissue. These results suggest that Ercc6l is a novel member of SNF2 family and may be crucial for development of embryo and tumor.