We introduce a novel measure of the market-wide rik of the interbank market: the total (across all banks) uncollateralized/collateralized lending volume ratio: MwideRiskInterB$MwideRiskInterB$. This measure is based on the intuition that lender banks should use less (more) uncollateralized (collateralized) lending when aggregate risk increases, after controlling for banks' features and market conditions that might affect MwideRiskInterB$MwideRiskInterB$ (e.g., banks' credit risk, cross-border inflows, supply-demand heterogeneity, and funding costs, among others). This is because collateralized loans are safer than uncollateralized ones after an interbank market-wide collapse. Actually, we show that MwideRiskInterB$MwideRiskInterB$ modifies the future lending decisions and net lending holdings of individual banks.