We analyzed mutations and CNVs in 25 SWI/SNF subunit genes (excluding nBAF-specific components from the analysis) making use of publicly available sequencing data for 408 [23] as well as 127 muscle-invasive bladder cancer samples [24] and identified ARID1A truncating mutations as the by far most common alterations in SWI/SNF complexes. The gene discussed is ARID1A; the disease is urinary bladder cancer.