This PhD thesis comprises three essays on the influence of the bank credit market on monetary policy transmission in Brazil. The first essay introduces a state development bank in a stochastic general equilibrium model featuring a financial accelerator as introduced by Bernanke et al. (1999). The development bank follows a simple linear rule defined according to government goals, instead of the competitive setup applied to the commercial banks. We calibrate the model to reproduce features of the Brazilian economy, and simulate different equilibrium situations involving cooperation or non-cooperation between central bank and development bank. We find that, in both cases, under reasonable restrictions on the scope of development bank actions, the development bank has some influence on macroeconomic stabilization, although small. The second essay tests the presence of a balance sheet channel of monetary policy transmission, using disaggregated data on working capital loans in Brazil, from 2003 to 2010. In order to identify financially constrained firms, we use firm size and the interest rates and risk classification of their previous loans. We perform linear and probit regressions to assess whether smaller and riskier firms present comparatively more pronounced declines on their bank loans following interest rate increases or GDP declines. In order to isolate the balance sheet channel from the bank lending channel, the statistical tests were performed separately on loan data from fifteen banks among the largest in Brazil. The results do not find statistically significant evidence of the balance sheet channel. The third essay examines empirically whether the level of bank capitalization has some influence on monetary policy transmission through a bank lending channel. We use a monthly bank data sample from December 2000 to May 2008 to assess whether the amount of credit supplied by poorly and well capitalized banks react differently to variations of the interest rate, and whether the reaction of poorly capitalized banks to interest rates is asymmetric. Panel data estimations using two different measures of bank capitalization do not find statistically significant evidence of these effects of bank capital on credit supply.