Serial whole body and lateral hindpaw magnification radiographs were obtained on 15 rats with collagen-induced arthritis. The radiographs were evaluated for findings of inflammatory arthritis. Soft tissue swelling and juxta-articular osteopenia usually developed two weeks after immunization. The swelling remained stable for the remaining seven weeks of the study, but the osteopenia apparently improved. Three weeks after immunization, erosions and periostitis began to develop in ten of the rats. These latter radiographic changes rapidly worsened over the next three weeks and then stabilized. The most frequent and severe changes were seen in the intertarsal, tibiotalar, and metatarsophalangeal joints. The toes, forepaws, and knees were infrequently involved. Other peripheral joints and the axial skeleton were spared. Five rats developed soft tissue swelling but had no articular erosions or periostitis. Serial radiography has potential usefulness for monitoring the effects of treatment in this experimental model for inflammatory arthritis.