Two groups, one of 824 adult diabetics and one of 320 age and sex matched non-diabetics, were examined for abnormal glucose metabolism and calcifications on anteroposterior shoulder x rays. Two hundred and sixty two (31.8%) of the diabetics had shoulder calcification compared with 33 (10.3%) of the control group, with a preponderant localisation in the right shoulder. Diabetes of long duration treated with insulin for a long time was associated with a larger percentage of shoulder calcifications. These data and previous laboratory findings suggest a possible pathogenetic correlation between the prevalence of calcific shoulder tendinitis and diabetes.