We investigate the optimal regulation of financial conglomerates which combine a bank and a non-bank financial institution. The conglomerate's risk-taking incentives depend upon the level of market discipline it faces, which in turn is determined by the conglomerate's liability strucure. We examine optimal capital requirements for standalone institutions, for integrated financial conglomerates, and for financial conglomerates that are structured as holding companies. For a given risk profile, integrated conglomerates have a lower probability of failure than either their standalone or decentralised equivalent. However, when risk profiles are endogenously selected conglomeration may extend the reach of the deposit insurance safety net and hen...