One hundred and seventy-three patients operated on for primary hyperparathyroidism over a four year period by one experienced surgeon are reviewed. An overall success rate of 98.8% was achieved with information from pre-operative localisation using ultrasound and parathyroid venography with sampling. Parathyroid ultrasound was heavily dependent on the experience of the operator. An experienced ultrasonologist detected 63% of solitary adenomas and correctly localised the site of 82%. Glands were not detected if they were of small size or in an inaccessible site. He identified all those enlarged glands over 0.36 grams in weight that were lying in the usual site. In contrast, inexperienced ultrasonologists had a detection rate of 20%. Parathyroid venography with sampling detected a single site of excess hormone production in the neck of 79% of patients with a single adenoma, and correctly localised the site in 75% of these. The side was correctly predicted for 63% of glands, the level was correctly predicted for 56% and both side and level localisations were correct in 44%. Multi-gland disease was correctly suggested by the experienced ultrasonologist in 56% of cases and by parathyroid venography with sampling in 31% cases.