In this paper, we construct alternative theoretical models for exchange rates by introducing additional risk factors, based on the volatility of macroeconomic fundamentals. The modified flexible-price monetary model is used to characterize the long-run equilibrium of exchange rates, while the modified sticky-price model explains the adjustment towards the long run. Empirically, in a number of OECD countries we find cointegration relationships between the exchange rate and macroeconomic variables and also some evidence for the long-run equilibrium error correction. Macroeconomic uncertainty can significantly explain the variation of the exchange rate from its fundamental-based value. The results lead us to believe that macroeconomic sources of FOREX risk may be a missing factor in the exchange rate study.