This paper develops a stochastic general equilibrium model of the federal funds market that incorporates non-Fisherian effects on interest rates stemming from both supply and demand shocks to reserves. Such a model may reconcile the widespread belief in a liquidity effect of money supply shocks with the difficulty many researchers have had in finding empirical support for such an effect. The model also cautions against interpreting the observed negative correlation between the federal funds rate and innovations to nonborrowed reserves as empirical confirmation of the ability of the Federal Reserve to lower short-term real interest rates.