1 This paper is ongoing research for my dissertation at UCLA. I want to thank my advisor Lee Ohanian and also Costas Azariadis and Gary Hansen for their valuable help and support. I also thank all the participants at the macro proseminars at UCLA for their comments and feedback. Special thanks to Rocio Mora at Banco de la Republica in Colombia for kindly providing the data. All errors are my own.Abstract I build a general equilibrium, Þnancial accelerator model that incorporates an explicit technology for the intermediary sector. A credit multiplier emerges because of a borrowing constraint that is a function of asset prices, internal funds and lending rates. With this Þnancial friction I show that small changes in the productivity and intermediation costs of banks generate large and persistent ßuctuations in economic activity. The transmission channel relies on the role that assets and internal funds play as collateral. After a negative shock hits Þnancial intermediation productivity, the resulting credit crunch and economic slowdown induce a fall in asset prices and internal fund accumulation. This further modiÞes the present and future volume of collateral, thereby amplifying and propagating the initial shock. I argue that changes in banking regulation in Colombia in the late 1990's increased intermediation costs, reduced banking productivity and induced a credit channel story that Þts the theoretical model presented here. This new regulation enhanced the credit crunch and economic slowdown that was already underway. Colombian data on loan/deposit interest rate spreads, credit volume, asset prices and economic activity support this argument.