Limited joint mobility and shoulder capsulitis were evaluated in 109 consecutive diabetic patients attending an out-patient diabetic clinic. Forty-nine had insulin-dependent diabetes mellitus (IDDM) and 60 had non-insulin-dependent diabetes mellitus (NIDDM). Seventy-five normal subjects were also examined. Limitation of joint mobility was detected in 24 (49%) patients with IDDM and in 31 (52%) patients with NIDDM but in only 17 (20%) normal subjects (p less than 0.001). There were no significant differences between diabetic patients with and without joint limitation with regard to age, sex, type of DM, mean daily insulin dosage and overall diabetic control as assessed by estimation of glycosylated haemoglobin concentration. However, patients with impaired joint mobility had a longer duration of diabetes (p = 0.01) and a significantly increased frequency of retinopathy compared to patients without joint limitation (p less than 0.05). Normal subjects with restricted joint mobility were older than those without restriction (p = 0.05). Shoulder capsulitis was present in 19% of patients with diabetes mellitus and 5% of normal subjects. However, there was no significant association between limited joint mobility and shoulder capsulitis in the diabetics.