Loss of SWI/SNF function has been associated with malignant transformation, and recent data demonstrate that several components of the SWI/SNF complexes, including ARID1A, ARID2, SMARCA4 (BRG1), SMARCB1 (SNF5), and PBRM1, function as tumor suppressors [2–4]. The gene discussed is SMARCA4; the disease is neoplasm.