One principal research in macroeconomics is concerned with the importance of nominal rigidities. This dissertation applies nominal rigidities in closed- and open-economy models to study issues on firms’ pricing decisions, optimal monetary policy in a financially constrained economy, and the choice of exchange rate regime in the presence of transfer problem. Chapter 1 presents empirical evidence for price and wage stickiness, and the development of models with nominal rigidities in macroeconomics and international finance. Chapter 2 incorporates state-dependent pricing in a closed-economy model to explain the asymmetric responses of output and prices to monetary shocks. The model focuses on the effects of strategic complementarity and substi...