Risk based regulation has emerged as the primary ingredient in the Basel-II proposals, where a bank capital is to become a direct function of a bank's riskiness. While the notion that bank capital be risk sensitive is intuitively appealing, the actual implementation, in the form of Basel-II, carries with it a host of potentially perverse side effects. Basel-II may increase financial risk, both for individual institutions and the entire banking system, and hence promote financial instability. This can happen, e.g., due to the endogenous nature of risk.