Refinement of in vivo tests.

It is important, both morally, scientifically and legally, that animal experimentation causes the minimum amount of suffering necessary to achieve the scientific objective. This paper describes an approach that facilitates the recognition and assessment of animal pain and distress through the use of clinical signs. The score sheet system can help to indicate new scientific responses, as well as to determine and to validate humane end points in the safety testing of biological products using animals. Some examples are given.