To clarify the pathogenesis of degenerative osteoarthrosis of the tarsometatarsal joints in hallux valgus, we evaluated dorsoplantar and lateral radiographs during weight-bearing in 16 patients (25 feet) with hallux valgus accompanied by degenerative osteoarthrosis of the tarsometatarsal joints and 25 controls (25 feet) with hallux valgus alone. The proximal second metatarsal articular angle (a parameter we devised), the hallux valgus angle, intermetatarsal angle, metatarsal length, sesamoid displacement, calcaneal pitch, and foot length were measured and then evaluation using a mapping system was performed. There were no significant differences in the hallux valgus angle, intermetatarsal angle, sesamoid displacement, calcaneal pitch, or foot length. In the presence of degenerative osteoarthrosis of the tarsometatarsal joints, the second, third, and fourth metatarsals were long, and a large inclination of the proximal articular surface of the second metatarsal and adduction of the first to fourth metatarsals were observed. These findings appeared to be involved in the development of this disorder.