This dissertation is a collection of three essays on misallocation and firm regulations. The first chapter investigates how size-dependent firm regulation policies can mitigate misallocation. The second chapter uses the same framework as the first to explore the intuition of a theoretically more subtle concept of misallocation. The third chapter analyzes a more specific firm regulation that targets at financial dealers. In chapter 1, I study the welfare implications of size-dependent firm regulation policies (SDPs) in the presence of entrepreneurial risks. Although SDP has been considered a source of misallocation, I show that, once entrepreneurial risks are taken into account, SDP might improve efficiency. Quantitatively, I show that...