Impairments in cardiovascular, respiratory and kidney function are considered as risk factors for complications following surgery. As the indication for surgery in asymptomatic primary hyperparathyroidism (HPT) is controversial, 123 patients undergoing surgery for HPT and 104 control subjects scheduled for common surgical procedures were evaluated preoperatively. Compared with the age- and sex-matched control group, serum calcium (P < 0.001), creatinine (P < 0.01) and glucose (P < 0.02) were all increased in the HPT group, while peak expiratory flow (PEF) was decreased (P < 0.04). Furthermore, the patients with HPT, compared with controls, were more often receiving antihypertensive medication (P < 0.005) and were more likely to have a history of congestive heart disease (P < 0.01), thromboembolic diseases (P = 0.05), stroke (P = 0.06) or diabetes mellitus (P < 0.02). Increased frequencies of ST-segment depression (P < 0.001) and T-wave abnormalities (P = 0.05) at electrocardiography together with an increased prevalence of heart enlargement visible at chest radiography (P < 0.01) were also seen in the HPT group when compared with the controls. All HPT patients and controls survived, but one HPT patient suffered a myocardial infarction in the post-operative period. In conclusion, the present study showed the pre-operative risk factor profile to be altered in HPT subjects with impairments in both cardiovascular and respiratory functions as well as in kidney function and glucose control. These findings should be kept in mind when the indications for surgery in asymptomatic patients with HPT are discussed.