The purpose of this article is to report the legal regulation and the main judicial decisions relating to the precautionary principle. In the Argentine system, unlike prevention, precaution did not enter in the new civil and commercial code as a principle applicable in any sector. It is expressly regulated in environmental matters and a group of authors extend it to other cases in which collective or diffuse interests exist. From a procedural perspective, caution has led to changes in the requirements of traditional legal instruments. The jurisprudence of all instances, including that of the Supreme Court of Justice of the Nation, shows that the configuration of the precautionary principle is still under construction.