Since 1986 it is required by law that animal trials be conducted only if they are "ethically justifiable". According to the German Animal Welfare Act, the criterion of ethical justifiability pertains to the question, if the harm caused to laboratory animals is proportional to the importance of the purpose of the experiment in which they are used (see Animal Welfare Act § 7a).

With regard to the concrete assessment of the harm, the Animal Welfare Act refers to Annex VIII of the European Directive 2010/63/EU. In this addendum, animal tests are classified into four categories of severity according to the degree of pain, suffering, distress or lasting harm they are inflicting on animals. The first category, "non-recovery", stands for experiments that are conducted completely under general anaesthesia from which the animal shall not recover consciousness. The remaining categories classify the harm caused by animal tests as "mild", "moderate" or "severe" depending on the degree and permanence of the resulting limitation of well-being for the animals in form of pain, suffering or distress.

The expected harm for test animals is weighed against the benefit that can result from the knowledge gained from an experiment. In the context of clinical trials this counterweight would be the therapeutic benefit for patients that could profit from the new treatment. Applicants for animal tests must declare the proportionality of the harm caused by a test in view of its purpose. The resulting assessment of ethical justifiability shall be verified by animal testing committees and the approval authorities in charge.