A new European Union (EU) directive with revised animal welfare standards for research has been approved by the European Union Parliament after two years of negotiation and compromise. The standards originally proposed and adopted by the European Commission were more stringent, including restrictions on the use of non-human primates, strong restrictions on re-using individual animals, and a ban on experiments which involve severe and prolonged suffering. The version finally approved by the European Union Parliament does not provide as many stringent protections for animals. The new standards mean that laboratories will have to get approval from national authorities for animal tests and that, if recognized alternatives exist, the laboratories must use them. While a general ban on the use of great apes, such as chimpanzees and gorillas, for scientific tests was adopted, the use of other primates, such as macaques, will be allowed. New categories of pain were adopted, ranging from “mild” to “severe,” which some believe will prevent repeated suffering by animals used in experiments. While the Commission originally proposed that only animals that were subject to mild pain be permitted to be used a second time, the final rule will allow the reuse of animals after tests involving “moderate” pain as well, in order to reduce the total number of animals used. The new animal welfare standards will have to be embraced by all EU member states, which will greatly benefit animals used in research in some member states, while it may have a negative impact elsewhere. According to EU law, member states cannot have laws more restrictive than those adopted by the EU. As a consequence, countries such as the United Kingdom, which has comprehensive animal welfare laws already in place, may have to lower their standards—and will be prevented from adopting new laws for the protection of animals in research.