A survey of the prevalence of Paget's disease in the United Kingdom (Barker et al., 1977) revealed 1225 patients with Paget's disease, detected in films of the lumbar spine, pelvis and femoral heads. These films and others obtained in these patients, have been analysed; 100 of the patients received full skeletal surveys. In these, the order of frequency of involvement was pelvis, lumbar spine, sacrum, femur, skull and dorsal spine. A similar distribution was found in those with incomplete surveys, with lower frequencies elsewhere in the skeleton. The extent of disease tended to increase with age. In the pelivs, the femora and the clavicles there was a right-sided bias; in the spine there were well-defined distributional differences. Of the patients with full skeletal surveys, 90% showed the disease in films covering the lumbar spine, pelvis and upper ends of femora and 31% had monostotic disease. The geographical and anatomical findings suggest that environment and stress are factors in the development of Paget's disease.