Does tariff liberalisation cause regulatory chill by putting downward pressure on health, safety and environmental standards? Or does it cause a race to the top as governments seek to use standards as non-tariff barriers to trade? There remains remarkably little empirical evidence to answer these long-debated questions. We seek to address this lack by analysing annual country-by-industry data on notifications of changes in sanitary and phytosanitary standards by WTO members. Our results show that own-tariff liberalisation and import pressure encourage a divergence in standards across countries. Regulatory chill in countries which have a low rate of notifications suggests a stuck-at-the-bottom problem, while countries with a high rate of notifications appear to race to the top.