Myelopathy is usually a late complication of AIDS, and until recently its symptoms were rarely recognized, masked by the general state of disability or the presence of other neurological complications. With prolonged survival and improved quality of life of HIV-infected patients, myelopathy is increasingly becoming a common source of disability. The cause of AIDS-myelopathy is unknown, but it is probably an indirect effect of the long-term presence of the HIV virus in the nervous system rather than the result of a direct infection. The purpose of this study is to determine whether methionine, an amino acid present in low doses in the normal diet, can improve myelopathy or stop its progression.