We aimed to identify all patients with postsurgical hypoparathyroidism (HypoPT) and to evaluate their risks of renal complications and cardiovascular disease in relation to their disease and its treatment. We identified possible patients through the Danish National Patient Registry and a prescription database. Case status was adjudicated by review of individual patients' hospital records. For each patient with postsurgical HypoPT due to surgery for nonmalignant diseases between 1988 and 2012, three age-matched (± 2 years) and gender-matched controls were selected from the general background population. The prevalence of postsurgical HypoPT was 22 per 100,000 inhabitants. We identified 688 patients who had undergone neck surgery since 1988 with subsequent hypocalcaemia and inappropriate low parathyroid hormone (PTH) levels that necessitated treatment with calcium and/or vitamin D supplementation for more than 6 months. The average age at diagnosis was 49 years (range, 17–87 years), and 88% were women. Sixteen percent of all patients had had neck surgery prior to the operation causing HypoPT. Compared with controls, patients with HypoPT had an increased risk of renal complications (hazard ratio [HR], 3.67; 95% confidence interval [CI], 2.41–5.59) and hospitalization due to seizures (HR, 3.82; 95% CI, 2.15–6.79), whereas there was no increased risk of cardiac arrhythmias (HR, 1.11; 95% CI, 0.79–1.57) or cardiovascular disease or death (HR, 0.89; 95% CI, 0.73–1.09). In conclusion, although risk of seizures and renal complications is increased, mortality and risk of cardiovascular diseases or arrhythmias is not increased in patients with HypoPT. Further study should try to determine how to reduce the risk of seizures and renal complications in HypoPT. © 2013 American Society for Bone and Mineral Research.