The clinical and laboratory parameters of calcific shoulder periarthritis (CSP) were examined in 900 patients with type II diabetes mellitus as well as in 350 age- and sex-matched control subjects. A threefold increased prevalence of CSP in diabetics compared with the control group was associated with the presence of longstanding and poorly controlled diabetes, hypercholesterolemia, and hypertriglyceridemia suggesting pronounced diabetic angiopathy, as well as with minor trauma and hypomagnesemia. Aging and serum calcium concentrations were not related to the presence of CSP. Thirty-two percent of diabetics with CSP were symptomatic; 15% of them presented with severe pain and restriction of shoulder movement. These findings confirm a close pathogenetic interrelation between CSP and diabetes mellitus.