We review arguments for and against reserve requirements and conclude that the main question is whether a distinction between money creation and intermediation can be made. We argue that such a distinction can be made in a money-in-advance economy and show that if the money-in-advance constraint is universally binding then reserve requirements on checkable accounts have no effect on intermediation. We then proceed to show that in a model in which trade is uncertain and sequential, a fractional reserve banking system gives rise to endogenous monetary shocks. These endogenous monetary shocks lead to fluctuations in capacity utilisation and waste. When the moneyin-advance constraint is universally binding, a 100% reserve requirement on checkable accounts can eliminate this waste.