This thesis investigates the determinants of trade policy. The first part studies the decision of developing countries on whether to take part in the Environmental Goods Agreement (EGA), an initiative by a subset of WTO members aimed at reducing tariffs on environmentally friendly goods. The second part, comprising two chapters, explores the determinants of export taxes. This policy instrument is especially interesting for two reasons. First, it is currently under-studied in the economic literature, and second, it is mostly unregulated by the WTO, and therefore demonstrates the way countries set their trade policy when they are free of external constraints.