The revised framework for capital regulation of internationally active banks (known as Basel II) introduces risk-based capital requirements. This paper analyses the relationship between bank capital, lending and macroeconomic activity under the new capital adequacy regime. It extends a model of the bank capital channel of monetary policy—developed by Chami and Cosimano—by introducing capital constraints à la Basel II. The results suggest that bank capital is likely to be less variable under the new capital adequacy regime than under the current one, which is characterized by invariant asset risk-weights. However, bank lending is likely to be more responsive to macroeconomic shocks.