We develop a dynamic general equilibrium model with an imperfectly competitive bank-loans market and collateral constraints that tie investors'credit capacity to the value of their real estate holdings. Banks set optimal lending rates taking into account the e¤ects of their price policies on their market share and on the volume of funds demanded by each customer. Lending margins have a signi…cant e¤ect on aggregate variables. Over the long run, fostering banking competition increases total consumption and output by triggering a reallocation of available collateral towards investors. However, as regards the short-run dynamics, most macroeconomic variables, including output, credit and housing prices, are more responsive on impact to exogenous shocks in an environment of highly competitive banks. The level of banking competition, through its e¤ects on endogenous lending margins, also a¤ects the degree of persistency of these variables. Speci…cally, stronger banking competition implies higher (lower) persistency after a monetary (credit-crunch) shock.