Background: Thyroid disease and hyperparathyroidism (HPT) are among the most common endocrine disorders, however, their association has not been well established. The aim of the present study was to determine the incidence of concomitant HPT in patients with thyroid disease requiring surgery, because a single definitive surgery should ideally be performed. Methods: We retrospectively reviewed a prospectively maintained database of patients who underwent thyroidectomy at a single institution. Data collected included the patients' initial indication for surgery, preoperative workup, and operative findings. Results: Of the 1,049 patients who underwent thyroidectomy, 56 (5%) had concomitant HPT and underwent simultaneous parathyroidectomy. Of these 56 patients, 36 initially presented with thyroid disease and 20 with HPT. The mean age was 59 ± 2 years, and 79% were women. The mean preoperative calcium and parathyroid hormone levels were elevated at 10.4 ± 0.1 mg/dL and 87 ± 7 pg/mL, respectively. Most of these patients had primary HPT (n = 54, 96%). Of the 36 patients presenting initially with thyroid disease, 26 had an elevated calcium or parathyroid hormone value and were preoperatively diagnosed with HPT. The remaining 10 patients had normal laboratory findings; however, a pathologically enlarged parathyroid gland was found at thyroidectomy. The overall cure rate for HPT within our series was 96%. Conclusion: The incidence of concomitant HPT in patients with thyroid disease requiring surgery is significant at 5%. Recognition of concurrent disease is important, because it allows for a single definitive surgery to treat both pathologies. © 2012 Elsevier Inc. All rights reserved.