This paper uses detailed data on bound and applied tariffs to assess the consequences of the May 2008 Modalities for the tariffs levied and faced by developing countries. We find that the tiered formula proposed for agriculture would halve tariffs in industrial countries and lower them more modestly in developing countries. In non-agriculture (NAMA), the formula will reduce the tariff peaks facing developing countries and cut average industrial country tariffs by more than a third. We use a political-economy framework to assess the likely use of flexibilities to reduce the size of the tariff cuts required on particular products and find they are likely to substantially reduce the outcome. Despite these flexibilities, there are likely to be worthwhile gains, with applied tariffs facing developing countries falling by about 19 percent in agriculture and 27 percent in NAMA.