This article offers a study to determine if the use of hydroxychloroquine in patients with rheumatoid arthritis can lessen the incidence of diabetes among this population. Antimalarials such as this drug have a long-standing safe and inexpensive history for treatment of autoimmune diseases and may improve glucose tolerance and prevent diabetes. The results of the study showed that among patients with rheumatoid arthritis, the use of hydroxychloroquine is associated with a reduced risk of diabetes. The study will follow up on the patients for 20 years.