Patients with rheumatoid arthritis will be seen at the NIH clinic on six separate visits (weeks 0, 1, 6, 12, 18, and 26) over 26 weeks. Week 0 is a screening visit. At weeks 1 and 26, patients will be admitted to the hospital for 24-hour blood sampling, DEXA scans, and brachial artery reactivity tests, as described above, plus X-rays of the hand and feet. After the first visit, they will start taking etanercept, given by self-injection under the skin (like insulin shots) twice a week. Follow-up visits at weeks 6, 12, and 18 will involve evaluations of disease activity and drug side effects through joint examination, blood tests, and questionnaires.