SMARCB1 (also known as SNF5, INI1, and BAF47), a subunit of SWI/SNF chromatin-remodeling complexes1,2, is biallelically inactivated in the vast majority (95%) of malignant rhabdoid tumors (RTs)3,4, aggressive and lethal cancers that predominantly strike young children. The gene discussed is SMARCB1; the disease is rhabdoid tumor.