Tariffication is an effort to convert all existing agricultural nontariff barriers (NTBs) to trade into bound tariffs and to reduce these tariffs over time. The main economic issues that arise with tariffication stem from the nonequivalence of tariffs in NTBs in a number of scenarios. This paper analyzes nonequivalence arising from the existence of imperfect competition in importing countries, price instability in importing and exporting countries, and inefficient allocation of quantitative restrictions. It is shown that in all these cases the definition of an appropriate "equivalent tariff" to be used in tariffication is not straightforward, and that in general this equivalent tariff cannot be computed on the basis of only observed price differences between countries.