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Desertification in the United States of America is very complex and difficult to combat on a continuing basis and on a large scale. It can be due to improper agricultural practices, livestock grazing, mining, fire management, recreation practices, deforestation, urbanization, and introduction of exotic species. Thus, national, state, and local policies must deal with a wide range of circumstances and land uses, and they must be comprehensive and dynamic, providing flexibility as issues, knowledge, and needs change. The United States can demonstrate many causations, but also successes, in combating desertification. However, much more work is needed to assure sustainable use of millions of hectares, particularly in the drylands of the western United States. A vigilance on policies and their implementation is required to assure that efforts to combat desertification are effective. Over time, some policies outlive their purpose and require change, but that is not always easy to achieve, and many times it takes a concentrated effort over several years or more to bring about, especially if that policy has its basis in law. Although this process sometimes seems slow, new laws continue to be enacted and policies are adopted that address land uses and the difficult task of combating desertification. Several examples are offered to show the variety of actions taken and processes used in the United States. (C) 1998 John Wiley & Sons, Ltd.