Background: Reports on adherence among patients with rheumatoid arthritis (RA) in Egypt and the Middle East region are lacking. This study aimed to measure adherence to treatment among a sample of patients with RA at Ain Shams University Rheumatology outpatient clinic and to assess factors affecting it. Methods: A cross-sectional descriptive study was carried out at the rheumatology outpatient clinic on a sample of 140 patients with RA. An interview questionnaire was used to measure adherence using the 8-item Morisky's scale, factors affecting adherence to treatment like patients satisfaction were assessed using the short form patient satisfaction questionnaire, also patients' knowledge, beliefs and rate of prescription refilling were assessed. Disease Activity Score - 28 was used as an objective method to assess RA disease activity. Results: According to Morisky's scale, 90.6% and 9.4% were classified as low and moderately adherent, respectively, none was classified as highly adherent to treatment. Important barriers to adherence reported were fear of side effects, nonavailability of free drugs in hospital pharmacy and cost of medications. Younger patients (P 0.002) and those reporting greater general satisfaction (P 0.02) were more likely to be adherent. In addition, on-time refill rates of medication (P 0.001) and disease activity (P 0.02) were associated with higher adherence scores and thus further validated the results of the adherence questionnaire. Conclusions: Higher adherence was associated with more positive beliefs on medication, greater satisfaction with health care and less disease activity.