Despite all the benefits, the use of animals in biomedical research is still a subject of debate with respect to its true value. The sensitivity of the community and the interest of scientists who work in the field of laboratory animal science and welfare have clearly demonstrated that the use of animals in biomedical research must be conducted under specific scientific, legal and ethical rules. The ethical justification of a research project starts from its initial designing phase until its completion and the review of the obtained results. Justification of the necessity of the project and the need to use animals in the interests of human or animal health, the importance of conducting a pilot study and a systematic review of previously published animal research on the topic, and the availability of the proper facilities, equipment and personnel are the main issues of concern in the ethical review of a research project. The ethical justification of the proposed project by the scientists themselves involves team-work, and should be a sustainable rather than a one-off procedure. This justification reflects the interest and the responsibility of scientists to reduce the number of animals, refine the procedures, and possibly replace animals in their research projects. The end-results of the ethical review process will be the creation of a trust relationship between scientists and society. .