Recent studies have demonstrated that subjects with low blood levels of vitamin D are at a higher risk of developing autoimmune diseases such as Rheumatoid Arthritis (RA). We are pursuing these studies to test the hypothesis that restoration of vitamin D levels ameliorates the manifestations of RA. We will test this hypothesis by inviting patients with RA to participate in a trial that examines the effects of oral vitamin D administration on the clinical expression of this disease. For this purpose, the participants of this trial will be asked to take an oral dose of 2,000 units of vitamin D daily for 6 months. We will examine the participant's joints, assess disease activity measures, and determine his/her blood levels of vitamin D before starting this treatment and periodically thereafter.