Crossover Study of Safety and Tolerability of Two Formulations of Adalimumab.

* Male or female subject age 18 years or older, who requires Humira 40 mg SC every other week (eow) or every week (ew) for the treatment of rheumatoid arthritis, in accordance with the local Humira label. * Subject must be a current, on-label user of Humira who rates his/her average Humira injection site related pain as at least 3 cm on a pain Visual Analogue Scale and has had at least 6 consecutive doses of Humira prior to Screening, or a biologic naïve subject who requires initiation of on-label treatment with Humira. * Subject has diagnosis of rheumatoid arthritis (RA) as defined by the 1987 revised ACR classification criteria or the ACR/EULAR 2010 criteria, * Female subjects are either not of childbearing potential, defined as postmenopausal for at least 1 year or surgically sterile (bilateral tubal ligation, bilateral oophorectomy and/or hysterectomy), or are practicing at least one method of birth control throughout the study and for at least 70 days after the last dose of study drug. * All female subjects of childbearing potential must have a negative test for pregnancy on a serum sample at Screening and prior to study drug dosing on a urine sample obtained at Visit 1.

* Subject has been treated with any investigational drug of a chemical or biologic nature within a minimum of 30 days or 5 half-lives (whichever is longer) of the drug prior to Visit 1. * Any infection(s) requiring treatment with intravenous (IV) anti-infectives within 30 days prior to Visit 1 or oral anti-infectives within 14 days prior to Visit 1. * Prior exposure to natalizumab (Tysabri®) or efalizumab (Raptiva®). * Known hypersensitivity to adalimumab or its excipients. * History of demyelinating disease (including myelitis) or neurologic symptoms suggestive of demyelinating disease.