Progressive hearing loss is a potential complication of Paget's disease, a metabolic disorder of accelerated bone formation and resorption. Calcitonin (Calcimar) is a recently introduced synthetic hormone used as a systemic treatment. Some studies have shown it to halt the progression of hearing loss. This is the first study of the effects of calcitonin on hearing loss to use a large number of patients with continuous use of the drug and long-term follow-up. It confirms that the drug is effective. We conducted chart reviews to compare the degree of hearing loss over time in 45 patients. Twenty-six patients have been taking salmon calcitonin for five to eight years to date and nineteen have received no treatment. Hearing loss was recorded at the initial examination (trial 1), one to four years later (trial 2), and then one to five years after the second evaluation (trial 3). Statistical analyses show a strong relationship between treatment and rate of hearing loss. The average hearing loss in the control group progressed from 47 dB in the first trial to 59 dB in the second trial to 75 dB in the third trial. Average hearing loss in the treated group remained at 47 dB over time. The difference in hearing loss over time between the two groups was less than 1 dB for the treated group and more than 28 dB for the control group. Results thus clearly show that calcitonin is effective in halting the progression of hearing loss in Paget's disease.