Protectionist instruments such as tariffs can distort the prices of traded goods. This paper explores the impact of specific (per-unit) duties on patterns of agricultural trade. Specific duties may encourage countries to export higher priced products, leading to an “Alchian-Allen effect” on unit values. Their restrictive effect on trade values is smaller for developed compared to developing countries. It can be explained by the specialization of these countries on low-priced products and by the low level of quality differentiation among their exports. Our results highlight the discriminating nature of specific duties for low-income countries.