Animal welfare in toxicity testing Animal welfare legislation is currently applicable in most countries to prevent misuse of animals in toxicological testing . In the U.S., the Animal Welfare Act as amended (7 USD, 2131-2156) provides guidelines and protection to animals used for scientific purposes including toxicity testing. In Europe, Directive 86/609/EC and 2003/65/EC have been recently on the principle of the 3Rs and aims to upgrade the minimum standards for laboratory animals by introducing appropriate animal welfare indicators and better training and information animal handlers. Furthermore, it is necessary that there is explicit and easy-to-follow documentation in each project license invol ving toxicological testing in animals,where the steps followed in the case of animal distress are described. Testing new chemical conpounds on vivo models can lead sometimes to pian, discomfort or animal distress. Animals exhibiting signs of suffering should be examined by a veterinarian or trained personnel and, if there is a good scientific reason to continue the study,administration of analgesics should be considered.