An avulsion fracture of the calcneous is rare, and we have treated two such cases. One case was a 52-year-old man, who had been treated for liver cirrhosis and diabetes mellitus for 4 years. He felt pain in the left heel while walking and was unable to walk. Radiographs showed osteoporosis and an avulsion fracture of the left calcaneus. Three weeks later, this fracture equally occurred in the right side. We have treated both cases conservatively. The other case was a 50-year-old woman, who had been conservatively treated for 3 weeks for the left 5th metatarsal bone fracture. She fell from bicycle in pes equinus position, and felt pain in the left heel and weakness of planter-flexion. Radiographs showed bone atrophy and an avulsion fracture of the calcaneus. At operation, the tendon was found to be entirely attached to the fragment, which was reduced and held by internal fixation. At present, they have no pain and no gait disturbance.