Radiography is commonly used to evaluate joint destruction in patients with rheumatoid arthritis (RA). However, radiography protocols for monitoring erosive progression in RA vary substantially between different hospitals. To evaluate the information provided by complete sets of hand and foot radiographs as compared with those of only some part of these extremities, the investigators analysed X-ray images from 2,193 patients with RA, comparing hands versus feet and right versus left. In cross-sectional analyses, joint-damage severity correlated strongly between left and right, but only weakly between the hands and feet. Disease would be incorrectly classified as non-erosive in 19.3% of patients if unilateral images were used, and in 24.0–40.4% of patients if hands were analysed without feet. Longitudinal analyses similarly showed that progression of RA would have been missed in 11.6–16.2% or 21.2–31.0% of patients, if using unilateral or solely hand images, respectively.