The chapter identifies the flat pyramid structure which allows Big Four firms to build on long and sometimes unpaid working hours of junior staff. The possibility of one of the Big Four failing is analyzed – as Arthur Andersen did. Despite attempts by the EU and the UK competition authorities, the degree of concentration of the audit market has increased. The smaller mid-tier firms may be withdrawing from the largest audits. The chapter introduces the key question ‘does size equal quality?’ and evaluates whether the Big Four are undertaking higher quality audits. Can smaller firms perform at the same level? Recent studies and our own evidence suggest that size matters. The chapter concludes with the first ‘quality axiom’: size is important and is equated with higher quality audits.