Parathyroid hormone levels (normal range 11-67 pg/ml) in the 15 pamidronate patients averaged 52±56 pg/ml. A chloride-to-phosphate ratio (Cl:Phos) of 33 or more is considered to be characteristic of hyperparathyroidism [11]. In the four patients with PTH levels of 60 pg/ml or more, the Cl:Phos ratio was 38±2. In the other 11 patients with a PTH of 45 or less, the Cl:Phos ratio averaged 30±9, (p=0.004). This evidence concerns the gene PTH and hyperparathyroidism.