In Italy, the accidental or intentional transplantation of crayfish species as part of the inland aquatic community is widespread and has produced many significant changes in the structure of the ecological community and the function of the ecosystem. The two Nearctic species, Procambarus clarkii and Orconectes limosus, have recently appeared as breeding populations in many northern and central Italian freshwater habitats, while there are scattered reports in the wild of Astacus leptodactylus and Pacifastacus leniusculus. Several aquaculture farms are cultivating exotic species, including the Australian Cherax destructor and C. quadricarinatus, without adequate precautions to prevent them from escaping. There are numerous risks for the native species, especially for the most widely distributed Austropotamobius pallipes (A. torrentium and Astacus astacus are reported in a few water bodies). Alien species can displace the native crayfish by direct and/or indirect competition and can transmit aphanomycosis or other diseases. Dangers for the ecosystem are also high. For example, in Lake Massaciuccoli (Tuscany), where studies are in progress, P. clarkii is destroying the submersed macrophytes, with heavy damage to the whole aquatic community. Moreover, its burrowing habit may result in structural deterioration of river banks and agricultural fields, as seen in the suburbs of Florence. Thus, homogenization of the Italian freshwater aquatic biota is underway and steps should be taken to slow this process. On October 23, 1997, the Italian government ratified the European Union directive 92/43/EEC Habitats. This new regulation is a great advance for crayfish conservation in Italy. New Regional Laws are to be drawn up according to the European directives and the native crayfish (now called by their specific names), although not designated as priority species, are recognized as species of interest for the EU and are subject to management actions. The new regulation declares that the introduction of alien species can be authorized only if a proper study has been conducted and only if the study has been favorably evaluated by the National Institute for Wild Fauna (INFS) or by another competent technical-scientific organization, 108assuring that neither natural habitats nor wild flora and fauna will be damaged. These Articles of the law focus on the primary actions capable of slowing the homogenization of Italian freshwater systems (or, from a more idealistic point of view, to stop it completely), i.e. that government authorities should: a) Promote the increase in scientific knowledge of the biology of both alien and native crayfish species, and b) Be able and ready to translate the acquired knowledge into practice.