When lenders experience unexpected losses, the supply of credit to borrowers can be disrupted. Researchers and policymakers have long sought estimates of how the availability of loans changes following a shock. The sudden oil price decline in 2014 offers an opportunity to observe precisely how affected lenders altered their portfolios. Banks that were involved with oil and gas producers cut back on some types of lending—consistent with traditional views of bank behavior. However, they expanded other types of lending and asset holdings with a bias towards less risky securities.