This paper uses an intermediation model to study the efficiency and welfare implications of both banks' minimum required capital–asset ratio and the regulation that limits, and in some countries forbids, banks' investments in the equity of nonfinancial firms. There are two sources of moral hazard in the model: one between the bank and the provider of deposit insurance, and the other between the bank and an entrepreneur who demands funds to finance an investment project. Among other things, the paper shows that capital regulation improves the bank's stability and can also be Pareto-improving. Equity regulation is never Pareto-improving and does not increase the bank's stability.