PURPOSE: To define the radiological features of the naviculo-medial cuneiform coalition. MATERIALS AND METHODS: This study examined 35 feet from 25 patients (mean age 26 years) with a naviculo-medial cuneiform coalition. The images were analyzed retrospectively with regard to irregular articular surface, subchondral sclerosis, subchondral cyst, beak-like spur, the change in joint space, bony fusion seen on plain radiographs (n=35) and CT (n=14), and the histological type of coalition on MRI (n=3). The extent of joint involvement was also evaluated. RESULTS: Of the 35 feet, plain radiographs and/or CT showed an irregular articular surface in 34 (97.1%), subchondral sclerosis in 30 (85.7%), a subchondral cyst in 29 (82.9%), a beak-like spur in 23 (65.7%), a narrowing of the joint space in 24 (68.6%) and no bony fusions (0%). The T1-weighted images revealed low signal intensity, and the T2-weighted fast spin-echo and gradient images revealed high signal intensity in the three feet with a cartilaginous coalition. The coalition involved the plantar part of the joint in all 35 feet. CONCLUSION: The characteristic radiological features of a naviculo-medial cuneiform coalition include an irregular articular surface with possible secondary degenerative changes in the plantar margin of the joint, non-osseous type.