The regulatory cycle view suggests that periods of deregulation encourage increased risk-taking, which in turn leads to financial crises and subsequent re-regulation. To test this proposition, we develop a novel 10-item index capturing prudential and structural banking regulation across 14 countries over the past century. We find that deregulation is indeed associated with heightened risk appetite and credit expansion. However, the regulatory response to financial crises has changed significantly over time. Consistent with the financial trilemma, the evidence suggests that the cycle has weakened, as open capital accounts are increasingly incompatible with effective regulation at the national level.