Current trends in the surgical treatment of primary hyperparathyroidism due to solitary parathyroid adenoma were evaluated in a questionnaire study. Response was obtained from 53 departments highly active in endocrine surgery in 14 countries (response rate 95%). Intraoperative histologic examination is widely (70%) regarded as necessary, but utilized more in North America and Scandinavia (87%) than elsewhere (45%). Intraoperative fat staining is used in one-third of the departments. Excisional biopsy including one whole gland is preferred by 32% to multiple incisional biopsies. Gross inspection of three normal parathyroid glands without histologic identification is favoured in 21% of the departments, while 31% prefer bilateral exploration and incisional biopsy. When an adenoma is found on the first side to be explored, 17% advocate bilateral exploration with incisional biopsy of all three normal glands, whereas unilateral exploration with excisional or incisional biopsy of the ipsilateral normal gland is preferred by a similar percentage.