 This is a double-blind, randomized, placebo-controlled, dose ranging study that will evaluate the safety, efficacy, and pharmacokinetic properties the absorption, distribution and excretion of aminopterin following oral administration by subjects with active rheumatoid arthritis 6 tender and 6 swollen joints who have not been treated with methotrexate MTX. Subjects are randomized to one of three treatments: placebo, 1 mg of LD-aminopterin, or 3 mg of LD-aminopterin in a 1:1:1 ratio. The study hypothesis is that the 3 mg LD-aminopterin per week is effective at treating rheumatoid arthritis compared to placebo. 