This thesis consists of three essays on firm dynamics. The first essay evaluates the effects of supply and demand shocks on firm dynamics and selection in Brazil. We explore the fact that China’s recent growth has led not only to an increase in import competition, but also to higher export demand for commodities, which is especially relevant in developing countries. We find that firms facing greater competition from Chinese imports suffer from an increase in exit probability, while firms in industries benefiting from increased export demand have lower probability of exit. In both cases, these effects are concentrated among smaller firms. In the second article, we describe the relationship between energy misallocation and resource misallocation across manufacturing industries in Brazil, and quantify the extent to which distortions affecting energy use result in output losses at the aggregate level. We find that these two measures of misallocation are positively related across industries, which suggests that energy is an important component of resource allocation efficiency. We show that reallocating resources between firms would result in substantial aggregate output gains. However, capital distortions account for most of the potential gains in manufacturing from reallocating resources between firms. The third essay compares firm life cycle dynamics in manufacturing and services, and finds that life-cycle growth is slower for service firms, even when controlling for initial size. We show that this result arises because of the selection pattern and weaker relationship between productivity and size in service industries. Finally, we assess the role of two potential explanations for these results: age-related distortions and monitoring costs.