A recent phenomenon is the rapid spread of anti-dumping laws amongst developing countries (i.e. China, India, Mexico). Between 1980 and 2003 the number of countries in the world with an anti-dumping law in place more than doubled, going from 36 to 97 countries. This paper examines a number of potential explanations for this proliferation of anti-dumping laws. We look for determinants explaining the timing of trade law adoption using a duration analysis. Results suggest that retaliatory motives are at the heart of the proliferation. This raises serious policy issues since anti-dumping laws should be about combating unfair trade, not about retaliation which runs contrary to the spirit of the WTO. Results also suggest that past trade liberalization raises the probability of a country to adopt an anti-dumping law. The proliferation of anti-dumping laws has important policy implications. In the interest of all users, anti-dumping rules should be renegotiated at the level of the WTO to make their use less easy, in order to avoid an escalation of protection worldwide.