This paper has been presented at a meeting of the National Research Council in February 1995, in Perugia, Italy. This is a preview of that which is to be the final product of the study: a manual for evaluating the environmental impact of pig-breeding farms. The most important issues in the environment-hog production relationship are discussed. After that, some elements for a sustainable swine production are focused. To solve the pig-breeding/environment conflict is not an easy task. The challenge is to find the right compromises, adopting all possible technologies for minimizing the impact on the environment. Since the first problem is the risk of water pollution due to manure, it is important to study the best solutions from the viewpoint of the watershed, taking into account the interactions and synergies occurring in the drainage system, and especially for the communities at the lower part of the basin. Therefore it becomes more and more of an absolute necessity to plan and manage resources using the watershed as a reference.