Background Preoperative epoetin-α administration is said to have a limited effect in patients with chronic inflammatory diseases such as rheumatoid arthritis (RA), due to lower iron availability. We studied the effects of preoperative epoetin-α treatment in orthopedic surgery patients in a daily life setting in which iron supplementation was assured, and compared the effects in RA and non-RA patients.Methods In an open, naturalistic, randomized controlled trial, 695 orthopedic surgery patients with preoperative hemoglobin (Hb) values of 10-13 g/dL, either with RA (113) or without RA (582), received either preoperative epoetin-α treatment added to standard care, or standard care alone. Hb values and transfusions were evaluated from entry into the study until 4-6 weeks after surgery.Results Both in RA and non-RA patients, perioperative Hb values were significantly higher and transfusion requirements were significantly lower in epoetin-α treated patients than in control patients (p < 0.001). In RA patients, the outcomes regarding Hb values were not significantly or relevantly different from non-RA patients.Interpretation Just as with orthopedic patients in general, RA patients benefit from preoperative epoetin-α treatment in combination with iron supplementation. We postulate that iron supplementation during epoetin-α therapy in RA patients is important for optimal efficacy.