The dissertation consists of three chapters in environmental economics and international trade. The first chapter identifies the effects of environmental regulation on Chinese manufacturing firms\u27 markups. Difference-in-difference and triple-differenced estimates show that more stringent environmental regulation decreases firms\u27 markups. Furthermore, environmental regulation has a significant impact on non-exporters\u27 markups, but it has no impact on exporters. Examining pre-trends, we find that SOEs did not change their behavior in anticipation of environmental regulation, but non-SOEs started to adjust before the regulation was implemented. The second chapter evaluates how the market size affects the impact of environmental string...