The current financial crisis has given rise to a new type of bank run, one that affects both the banks' assets and liabilities. In this paper we combine information from the commercial paper market with loan level data from the Survey of Terms of Business Loans to show that during the 2007-2008 financial crises banks suffered a run on credit lines. First, as in previous crises, we find an increase in the usage of credit lines as commercial spreads widen, especially among the lowest quality firms. Second, as the crises deepened, firms drew down their credit lines out of fear that the weakened health of their financial institution might affect the availability of the funds going forward. In particular, we show that these precautionary draw-downs are strongly correlated with the perceived default risk of their bank. Finally, we conclude that these runs on credit lines have weakened banks further, curtailing their ability to effectively fulfill their role as financial intermediaries.