The Federal Reserve Board published research examining how the Volcker Rule affected trading revenue at the 21 largest US trading firms during a 100-day stress period centered on the COVID-19 financial crisis. The paper finds that, despite elevated market volatility, trading profits were consistent with volume-driven fees and commissions and with widening bid-ask spreads. Using a novel data collection, the study adds to evidence that the Volcker Rule’s effects on trading-related revenue are associated with increased financial stability and reduced exposure to market shocks.