The contribution of biomedical sciences to the scientific breakthroughs in the last years has benefitted also by experiments on animals. As for diagnostic imaging, the use of new contrast media for angiography, CT and MRI makes it necessary, according to the law, to perform preliminary animal studies to test efficacy, pharmacokinetics and pharmacodynamics of the contrast agents. Experimental animal studies of clinically well-established contrast agents are also justified by the need to implement new imaging modalities. The close relationship between medical research and animal experimentation has awakened public opinion, as well as the researchers themselves, to the ethical and legal problems related to animal testing. This paper reports on the regulations which are currently in use in this field.