AbstractRadiological observations in 28 patients with Paget's disease of bone treated for 10–40 months with synthetic human calcitonin are presented. A method of evaluating and scoring radiological changes was devised. The results suggest that response to treatment is dose-related. No patient on a dose of 0·5 mg twice daily showed evidence of deterioration and five showed improvement. On a dose of 0·5 mg a day, three patients improved and four deteriorated. On 0·5 mg a week, four patients deteriorated and none improved.