The incidence of the ectopic parathyroid glands seems to be different between normal subjects and patients affected by primary hyperparathyroidism. We reviewed a serie of patients operated on for primary hyperparathyroidism in our Institute between 1985 and 1991, and the reports from literature about this mean; the frequence of ectopies is = 31% (10.3% in the upper- anterior mediastinum). These findings are similar to those reported in the literature. The higher incidence of ectopies in the hyperparathyroid group respect to the normal one and the surgical problems that it could cause represent a reinforcement of the concept that parathyroid surgery should be done only by an experienced, technically and theoretically prepared surgeon, and may justify the use of non invasive, non expensive imaging techniques at the first cervical exploration for suspected hyperparathyroidism, in order to ameliorate the results and in particular to solve suddenly some dramatical cases due to major parathyroid ectopies.